HP Continuous Access Journal User Manual

HP P9000 Continuous Access Journal User Guide

Abstract

This guide explains how to use HP P9000 Continuous Access Journal Software to replicate data between local and remote HP P9000 disk arrays and to achieve disaster tolerance with maximum application performance. Topics include setting up remote copy connections, configuring the storage system, creating and monitoring remote copies, recovering from a disaster, and troubleshooting. The intended audience is a storage system administrator or authorized service provider with independent knowledge of HP P9000 disk arrays and the HP Remote Web Console.

HP Part Number: AV400-96399 Published: September 2011 Edition: Fifth

Confidential computer software. Valid license from HP required for possession, use or copying. Consistent with FAR 12.211 and 12.212, Commercial Computer Software, Computer Software Documentation, and Technical Data for Commercial Items are licensed to the U.S. Government under vendor's standard commercial license.

The information contained herein is subject to change without notice. The only warranties for HP products and services are set forth in the express warranty statements accompanying such products and services. Nothing herein should be construed as constituting an additional warranty. HP shall not be liable for technical or editorial errors or omissions contained herein.

Acknowledgements

Microsoft®, Windows®, Windows® XP, and Windows NT® are U.S. registered trademarks of Microsoft Corporation.

UNIX® is a registered trademark of The Open Group.

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Revision History

DescriptionDateEdition

Applies to microcode version 70-01-01-00/00 or later.October 2010First

Applies to microcode version 70-01-24-00/00 or later.November 2010Second

Applies to microcode version 70-01-62-00/00 or later.January 2011Third

Applies to microcode version 70-02-01-00/00 or later.May 2011Fourth

Applies to microcode version 70-02-5x-00/00 or laterSeptember 2011Fifth

Contents

1 Continuous Access Journal overview ............................................................8

Continuous Access Journal software ...........................................................................................8

How Continuous Access Journal works........................................................................................8

Hardware and software components...........................................................................................9

P9500 storage systems.......................................................................................................10

Main and remote control units .......................................................................................10

Pair volumes......................................................................................................................11

Journal volumes.................................................................................................................11

Journals............................................................................................................................11

Data path.........................................................................................................................12

Consistency groups and journals..........................................................................................12

Remote Web Console.........................................................................................................12

RAID Manager..................................................................................................................13

Overview of copy operations...................................................................................................13

Initial copy operation ........................................................................................................13

Update copy operation ......................................................................................................14

Read and Write I/O operations during remote copy operation.....................................................15

S-VOL write option..................................................................................................................15

Difference management...........................................................................................................15

Pair status..............................................................................................................................15

2 Requirements and specifications.................................................................17

System requirements................................................................................................................17

3 Planning volumes and systems....................................................................20

Plan and design workflow .......................................................................................................20

Assessing business requirements for data recovery .....................................................................20

Determining your RPO .......................................................................................................21

Write-workload .....................................................................................................................21

Measuring write-workload...................................................................................................21

Sizing journal volumes ...........................................................................................................22

Determining the required journal volume capacity..................................................................22

Calculating the journal size.................................................................................................23

Planning journals ..............................................................................................................23

Data transfer speed considerations ..........................................................................................23

RAID group configuration ...................................................................................................24

Fibre Channel port configuration..........................................................................................24

Planning journal volumes ........................................................................................................24

Planning pair volumes ............................................................................................................25

Maximum number of pairs allowed .....................................................................................25

Calculating maximum number of pairs.............................................................................25

Priority set for initial copy operations and scheduling order.....................................................26

Disaster recovery considerations ..............................................................................................28

Host failover software ........................................................................................................28

Sharing volumes with Continuous Access Synchronous, other program products..............................28

Planning for Continuous Access Journal with multiple P9500 systems ............................................29

Multiple journals per RAID Manager consistency group .........................................................29

Planning for previous models ...................................................................................................31

Guidelines for preparing systems for Continuous Access Journal ...................................................32

System option modes .........................................................................................................33

4 Planning the data path..............................................................................35

Data path design workflow .....................................................................................................35

Contents 3

Sizing bandwidth ..................................................................................................................35

Five sizing strategies ..........................................................................................................35

Calculating bandwidth ......................................................................................................36

Sizing bandwidth for peak write-workload........................................................................36

Sizing bandwidth for peak rolling average write-workload..................................................37

Latency .......................................................................................................................38

Packet loss ...................................................................................................................38

Planning ports for data transfer ................................................................................................39

Determining required number of ports ..................................................................................39

On setting up ports ...........................................................................................................40

Distances supported for Fibre Channel type, number of switches ..................................................40

Supported data path configurations .........................................................................................41

5 Configuration operations...........................................................................43

Configuration workflow ..........................................................................................................43

Define Fibre Channel port attributes .........................................................................................43

Configure storage systems for Continuous Access Journal, define logical paths ...............................45

Configure additional logical paths ...........................................................................................47

Specify number of volumes for initial copy, resync ......................................................................48

Register journal volumes in a journal ........................................................................................50

6 Pair operations.........................................................................................53

Pair operations workflow.........................................................................................................53

Check pair status....................................................................................................................53

Create the initial copy ............................................................................................................53

Split a pair ...........................................................................................................................57

Split a mirror .........................................................................................................................59

Create a point-in-time copy .....................................................................................................59

Restore a pair .......................................................................................................................60

Resynchronize a mirror ...........................................................................................................62

Delete a pair ........................................................................................................................63

Delete pair volumes from a mirror ............................................................................................65

7 Monitoring the system...............................................................................67

Monitor pair activity and status................................................................................................67

Pair status definitions..........................................................................................................67

PSUS types and behaviors..............................................................................................71

PSUE types and behaviors..............................................................................................72

Filtering Information in the List in the Pair Operation window...............................................73

Saving pair status information into a text file.....................................................................74

Monitor copy operations data, I/O .....................................................................................75

Select data to be graphed..............................................................................................76

Manipulate graph, save data..........................................................................................78

Monitor journal (mirror) status...................................................................................................78

Mirror status definitions.......................................................................................................78

Monitor logical path status.......................................................................................................79

History of operations for data volume pairs...........................................................................80

8 Maintaining the system ............................................................................81

Pair maintenance—change the pair-split option .........................................................................81

Journal and mirror maintenance...............................................................................................81

Change Continuous Access Journal options used by journals ..................................................82

Change Continuous Access Journal options used by mirrors ....................................................84

Delete journal volumes from a journal ..................................................................................86

Delete a journal ................................................................................................................87

Logical path maintenance........................................................................................................87

Modify data-transfer time threshold .....................................................................................87

4 Contents

Delete logical paths ..........................................................................................................88

Delete the logical path between primary and secondary storage system ...................................89

Manage power-off for systems and network devices ...................................................................89

When power stops unexpectedly.........................................................................................89

When power is removed from primary or secondary system................................................90

When power is removed from network relay devices .........................................................90

Power off storage systems intentionally..................................................................................90

Power off the primary or secondary system.......................................................................90

Power off the primary and secondary systems at the same time...........................................90

Power off network relay devices...........................................................................................91

9 Disaster recovery operations .....................................................................92

Preparing for disaster recovery ................................................................................................92

File and database recovery procedures ....................................................................................92

Switch operations to the secondary site ....................................................................................92

Copy data back to the primary site ..........................................................................................92

Resume normal operations at the primary site ............................................................................93

Disaster recovery when the system consists of multiple primary and secondary storage systems.........94

Recovering the primary site from a failure when the system consists of multiple primary and

secondary storage systems..................................................................................................94

Transferring business tasks to primary site after recovering from primary site failures...................94

Recovery procedures with shared volumes..................................................................................95

Recovery in a 3DC cascade configuration ............................................................................96

Recovering from primary site disaster in 3DC multitarget configuration......................................96

Recovering from primary site failures (when delta resync operation is performed)........................98

Recovering from failures in the primary site and the Continuous Access Synchronous secondary

site................................................................................................................................100

Recovery in a 2DC configuration ......................................................................................101

Resume operations in the primary site ...........................................................................101

Recovery with Business Copy configuration .........................................................................102

10 Troubleshooting....................................................................................103

General troubleshooting........................................................................................................103

Troubleshooting logical paths ................................................................................................104

Troubleshooting suspended pairs ...........................................................................................106

Troubleshooting using Remote Web Console............................................................................107

Error codes .........................................................................................................................108

Troubleshooting using RAID Manager ....................................................................................108

Service information messages (SIMs) ......................................................................................119

Miscellaneous troubleshooting................................................................................................121

Suspension among journals ..............................................................................................121

11 Support and other resources...................................................................122

Contacting HP......................................................................................................................122

Subscription service..........................................................................................................122

Documentation feedback..................................................................................................122

Related information...............................................................................................................122

HP websites....................................................................................................................123

Conventions for storage capacity values..................................................................................123

Typographic conventions.......................................................................................................123

A Sharing Continuous Access Journal volumes ..............................................125

Volume types that can be shared with Continuous Access Journal................................................125

LUN Expansion....................................................................................................................127

Virtual LUN .........................................................................................................................127

Cache Residency..................................................................................................................127

Auto LUN............................................................................................................................127

Contents 5

LUN Manager......................................................................................................................128

Thin Provisioning .................................................................................................................128

Data Retention ....................................................................................................................128

Performance Monitor ............................................................................................................129

B Continuous Access Journal configurations with Continuous Access

Synchronous.............................................................................................130

Sharing volumes with Continuous Access Synchronous...............................................................130

3DC cascade configuration ..................................................................................................131

Prerequisite information for 3DC cascade ...........................................................................131

Procedure for setting up 3DC cascade ...............................................................................132

3DC multitarget configuration ................................................................................................132

Prerequisite information for 3DC multitarget ........................................................................133

Procedure for setting up 3DC multitarget.............................................................................133

Delta resync configuration .....................................................................................................134

Prerequisite information for creating the delta resync pair .....................................................135

Prerequisite information for performing the delta resync operation..........................................135

Creating a delta resync pair .............................................................................................137

Configuring the delta resync operation environment to support remote command devices..........137

Establish immediate communications ............................................................................137

Assign mirrors to remote command devices ....................................................................138

Release a remote command device which is assigned to a mirror......................................140

Perform the delta resync operation .....................................................................................140

2 data center configuration ...................................................................................................140

Prerequisite information for 2DC configuration ....................................................................141

Specifications and restrictions for Continuous Access Journal pair operations.......................141

Specifications and restrictions for Continuous Access Synchronous pair operations...............142

Procedure for 2DC setup ..................................................................................................142

C Continuous Access Journal configurations with Business Copy......................143

Overview............................................................................................................................143

Configurations with Business Copy primary volumes .................................................................143

Configurations with Business Copy secondary volumes .............................................................145

Pair status and data currency.................................................................................................145

D Continuous Access Journal configurations with External Storage Access

Manager..................................................................................................147

Overview............................................................................................................................147

Configurations with Continuous Access Journal secondary volumes ............................................147

E Continuous Access Journal GUI reference...................................................148

Journal Operation window ....................................................................................................148

Journal Detail window ..........................................................................................................151

Change Journal Option dialog box ........................................................................................154

Change Mirror Option dialog box .........................................................................................154

Edit Journal Volumes dialog box.............................................................................................155

Pair Operation window ........................................................................................................157

Detailed Information dialog box ........................................................................................160

Paircreate dialog box ......................................................................................................163

Pairsplit-r dialog box .......................................................................................................165

Pairresync dialog box ......................................................................................................166

Pairsplit-S dialog box .......................................................................................................167

Change Pair Option dialog box.........................................................................................168

Display Filter dialog box ..................................................................................................169

DKC Operation window .......................................................................................................170

Remote Systems Information ..............................................................................................171

6 Contents

Logical Path Information....................................................................................................172

Port Information for the local system....................................................................................173

DKC Status dialog box ....................................................................................................173

Add DKC dialog box .......................................................................................................175

DKC Option dialog box ...................................................................................................176

Usage Monitor window ........................................................................................................177

History window ...................................................................................................................177

Operations in History window ..........................................................................................179

History window notes.......................................................................................................180

Export operations history .................................................................................................181

Optional Operation window .................................................................................................181

Glossary..................................................................................................183

Index.......................................................................................................185

Contents 7

1 Continuous Access Journal overview

Unless otherwise specified, the term P9000 in this guide refers to the following disk array:

• P9500 Disk Array

The GUI illustrations in this guide were created using a Windows computer with the Internet Explorer browser. Actual windows may differ depending on the operating system and browser used. GUI contents also vary with licensed program products, storage system models, and firmware versions.

With Continuous Access Journal (Cnt Ac-J), you create and maintain a remote copy of a data volume on a P9500 system. The remote copy is a block-for-block copy of the local storage volume. Remote data is consistent with local data and therefore available for recovery of the local volume should the need arise.

This guide provides instructions for planning, implementing, operating, maintaining, and troubleshooting a Continuous Access Journal system.

The following configurations described in this document are unsupported in version 70-01-2x:

• Three data center (3DC) multitarget configuration

• Three data center (3DC) cascade configuration

• Three data center (3DC) configuration using the delta resync function

• Configuration using multiple primary and secondary storage systems

Continuous Access Journal software

With Continuous Access Journal, application data is copied to a secondary P9500 system at a remote location. Continuous Access Journal is designed to support a remote site hundreds and even thousands of miles from the local site, making recovery from region-wide disasters possible. This guide provides scenarios and procedures for disaster recovery from multiple sites.

When a pair is created, the remote system will contain an asynchronous, block-for-block copy of the local storage volume. Impact on host I/O and the primary storage system is limited, since updates sent to the primary volume are also copied to a local journal volume. The remote system “pulls” data from the journal volume across the communication link to the backup-volume. The primary system is free to perform its role as a transaction processing resource rather than as replication engine.

How Continuous Access Journal works

With Continuous Access Journal, you enable a data back up from a primary volume (P-VOL) on the local system to a secondary volume (S-VOL) on a remote system. Continuous Access Journal operations are performed sequentially as shown below.

Figure 1 Basic sequence in Continuous Access Journal operations

8 Continuous Access Journal overview

Remote replication occurs using journal volumes on the local and remote systems.

• The journal on the local system is the “master journal”.

• The journal on the remote system is the “restore journal”.

Replication occurs in the following sequence:

• Journal obtain - When the host sends an update to the primary volume, the system’s

journal-obtain function triggers a copy of the update data to the master journal volume.

◦ The host assigns write-sequence numbers to the data sent to the journal. ◦ Write-sequence numbers and other metadata attached to journal data insure consistency

with the data in the primary volume.

• Journal copy - data is copied from the master journal to the restore journal.

If the master journal has data, the primary system transfers it to the restore journal. When data transfer is complete, master journal data is discarded.

◦

◦ Data copy to the restore journal is initiated by the read-journal command issued by the

remote system.

◦ Data copy occurs on a continual basis unless there is no data in the local journal. On

storage system, journal reading operations are performed just after finished the former read operation.

• Journal-restore - the secondary volume is updated with changed data from the restore journal.

Data is copied to the secondary volume according to the write sequence numbers, insuring data consistency.

◦

◦ When journal-restore is completed, the data in the restore journal is discarded.

NOTE:

• In the configuration of Continuous Access Journal, the updating of data volumes and the

creating of journal data are processed. The performance of data volumes replicated with Continuous Access Journal will be slightly lower than that of unreplicated data volumes.

• The primary storage system does not remove the target journal data from its master journal

volume until it receives the sequence numbers of the restored journal that is given to the read journal command from the secondary storage system. This is true even if the primary storage system and secondary storage system are connected using a channel extender product.

Hardware and software components

A typical configuration consists of a P9500 or externally attached system on both local and remote sites, a host or hosts connected to the systems, Continuous Access Journal software on both systems, data path connections, and interface tools for configuring and managing Continuous Access Journal.

• The local and remote P9500 systems are connected using dedicated fibre channel data paths,

which can include fibre channel switches. Data paths are routed from the fibre channel ports on primary system to the ports on the secondary system.

• The host is connected to the P9500 using a fibre channel target port.

• Remote Web Console is connected via a management LAN.

Hardware and software components 9

A Continuous Access Journal system consists of the following:

• P-VOLs and S-VOLs on the local and remote P9500

• Master and restore journal volumes on the local and remote P9500

• Master and restore journals on the local and remote P9500

The master journal consists of the primary volume(s) and master journal volume(s).◦

◦ The restore journal consists of the secondary volume(s) and restore journal volume(s).

Management software consists of:

• Remote Web Console graphical user interface (GUI)

• RAID Manager

NOTE:

• Continuous Access Journal Z processing continues uninterrupted if the SVP reboots or even if

the SVP fails.

• Continuous Access Journal Z does not support operations in which one P-VOL is copied to

more than one S-VOL, or more than one P-VOL is copied to one S-VOL.

Continuous Access Journal components are illustrated in the following figure and described in greater detail in the following sections.

Figure 2 Continuous Access Journal components

P9500 storage systems

Continuous Access Journal is operated using two P9500 storage systems, one at the primary and one at secondary sites. The primary system consists of the main control unit (MCU) and the SVP . The secondary system consists of the remote control unit (RCU) and the SVP.

• The primary system communicates with the secondary system over dedicated fibre channel

remote copy connections.

• The P9500 system can function simultaneously as a primary and secondary system.

Main and remote control units

The primary and secondary systems are often referred to as the MCU (primary system) and RCU (secondary system). MCU is the main control unit, RCU is the remote control unit.

10 Continuous Access Journal overview

MCUs control the primary storage volume (P-VOL) and the following operations:

• Host I/O operations to the P-VOL

• Master journal operations

• Initial copy and update copy operations between the P-VOL and secondary volume (S-VOL).

RCUs control the secondary storage volume (S-VOL) and the following operations:

• Issue read-journal commands to the MCU.

• Manage the copying of journal data from master to restore journal.

• Manage the copying of restore journal data to S-VOL.

• Assist in managing pair status and configuration (for example, rejects write I/Os to the S-VOLs).

Pair volumes

Original data is stored in the P-VOL and the remote copy is stored in the S-VOL. The pair can be paired, split, re-synchronized, and returned to the simplex state. When synchronized, the volumes are paired; when split, new data sent is to the P-VOL but held from the S-VOL. When re-synchronized, changed data is copied to the S-VOL. When a disaster occurs, production operations can be transferred to the S-VOL. When the primary site is functional again, operations and data can be transferred and copied back to the P-VOL.

The P-VOL remains available to the host for read and write I/O operations. The secondary system rejects write I/Os for the S-VOL, unless the write-enable option is specified for the S-VOL. Then, write I/O is allowed to the S-VOL while the pair is split. In this instance, S-VOL and P-VOL track maps keep track of differential data and use it to re-synchronize the pair.

Journal volumes

Journal volumes are required on the primary and secondary systems.

• Updates to the P-VOL are copied to the master journal volume in the primary system. See the

illustration in “Journals” (page 11).

• Master journal data is copied to the restore journal volume on the secondary system.

• Journal volumes can have different volume sizes and different RAID configurations.

• Journal data is stored sequentially and separately into each journal volume in the same journal.

For information on planning journal volumes, see “Sizing journal volumes ” (page 22) .

NOTE: If a path is defined from a host to a volume, you cannot register the volume as a journal

volume.

Journals

Journals help you manage data consistency between multiple P-VOLs and S-VOLs. A journal consists of two or more data volumes and journal volumes.

You use journals to create multiple pairs and to split, resync, and release multiple pairs. Journals are required on the primary and secondary systems.

Each data volume and its associated journal volume reside in the same journal. This is illustrated below.

• The master journal contains master journal volumes and is associated with the P-VOL.

• The restore journal contains restore journal volumes and is associated with the S-VOL.

Each pair relationship between journals is called a "Mirror". A Mirror ID identifies a pair relationship between journals. When the pair is created, it is assigned a mirror ID.

Hardware and software components 11

Figure 3 Journals

Data path

The physical transmission link between the local and remote systems is called the data path. Continuous Access Journal commands and data are transmitted through the fibre channel data path and switches. The data path is connected to the primary and secondary systems through two types of Fibre Channel ports, Initiator and RCU Target ports.

One data path connection is required for Continuous Access Journal. HP recommends two or more independent connections to provide hardware redundancy. A maximum of eight paths can be used.

For more information, see “Planning the data path” (page 35).

Consistency groups and journals

A consistency group is a group of pairs in the same primary and secondary systems. Consistency groups are defined using RAID Manager. When you issue a pair command, the copy operation is executed on all pairs in the group with the writing order guaranteed between a primary volume and the secondary volume. The pair status changes at the same time, depending on group options.

Continuous Access Journal can use RAID Manager consistency group numbers. Therefore, you can create a Continuous Access Journal pair using the consistency group numbers from RAID Manager. In Continuous Access Journal operations, the consistency group numbers that are specified from RAID Manager are assigned to journal numbers.

The specification of consistency group number storage system has total 256 consistency groups (numbered 0 to 255) for the P-VOL and S-VOL (No. 0 to 127 are assigned).

Journals are used in Continuous Access Journal to guarantee data consistency across multiple pairs. For Continuous Access Journal operations, it is best practice to make consistency group numbers and journal numbers the same, if possible.

NOTE: The consistency group number of the primary and secondary data volumes to be paired

must be same.

Remote Web Console

Remote Web Console communicates with the SVP of each storage system over defined TCP/IP connections.

• Remote Web Console must be LAN-attached to the primary system

• Remote Web Console is not required on the secondary system; however having it available

allows you to change Continuous Access Journal parameters and access the Continuous Access Journal S-VOL for maintenance or disaster recovery.

12 Continuous Access Journal overview

NOTE:

• Administrator or Continuous Access Journal write access to the Remote Web Console Java

applet program is required to perform these operations. Users without Administrator or Continuous Access Journal write access can only view Continuous Access Journal information.

• If the RAID Manager computer is not installed, contact your HP account team for information

on Continuous Access Journal configuration services.

RAID Manager

RAID Manager can be used to perform the same operations as the Remote Web Console GUI. The operations can be run with RAID Manager using scripts.

Overview of copy operations

The following sections describe initial and update copy operations including the underlying operations, such as journal processing and differential data management.

Initial copy operation

The initial copy is executed when the primary storage system copies all the data in sequence in the P-VOL directly to the S-VOL. Though journal volumes are not used during the initial copy, the copy data in this operation is referred to as “base journal data”.

• Creating pairs independently of journal activity results in the base journal data being copied

to the respective S-VOLs one-at-a-time. This extends the time required for multiple initial copies.

• An initial copy operation can be performed to establish the Continuous Access Journal pair

relationship — with no data copied between the volumes. This can be done when data in the P-VOLs and S-VOLs are the same.

• A volume pair can also be created using a Continuous Access Synchronous initial copy

operation. See “Planning pair volumes ” (page 25) for more information.

Overview of copy operations 13

NOTE:

• If you manipulate volumes (not journals) to create or resynchronize two or more data volume

pairs within the same journal, the base journal data for these pairs will be stored in the restore journal. Therefore, the operation for restoring the latter base journal will be delayed.

• You can specify None as the copy mode for initial copy operations. If the None is specified,

initial copy operations are not performed. Therefore, if you specify None, you are responsible for ensuring that the data in the primary and secondary data volume is exactly the same.

• You may create a Continuous Access Journal data volume pair by using Continuous Access

Synchronous initial copy. In that case, set the appropriate system option that is system option 474, on both primary and secondary storage system. In addition, the script, which is written especially for this operation, is also required. If you use the script without setting the system option on the secondary storage system, the storage system recognizes the Continuous Access Synchronous R-VOL as the Continuous Access Journal S-VOL, and the SSB log (SSB=CBED) is generated in the secondary storage system. In this case, the command to create the pair is rejected. The script is executed normally when you use the script without setting the system option on the primary storage system, however, note that the processing speed of the Continuous Access Synchronous initial copy slows down if there is the update I/O during the operation.

• If you delete all Continuous Access Journal data volume pairs in the journal and then create

a Continuous Access Journal data volume pair, wait for one or more minutes after deleting pairs.

• When an RCU is shared with multiple MCUs, perform the pair resume operation after system

option mode 593 is set to available if you resume 1025 or more pairs from multiple MCUs (range: mirror) at the same time. Pair resume operations may fail if system option mode 593 is not available.

Update copy operation

When a host produces new or changed information, the following occurs in the primary storage system:

• The update is written to the P-VOL.

• The update is copied to the master journal along with metadata that includes sequence and

other consistency information. Replication to the secondary system is prompted by the read-journal command. This is issued

by the remote system independently of host I/O activity. Read-journal commands are repeated every 30 seconds. At this time, the following occurs:

◦ Any data that exists in the master journal on the primary side is sent to the restore journal

on the remote system.

◦ The updated data is then copied to the S-VOL. ◦ Data is updated to the remote system continuously until there is no more data in the master

journal.

◦ Journal data on the primary and secondary systems is discarded when data consistency

is established in the copy.

NOTE: Journal data is transferred using special I/O operations initiated by the secondary

system (RCU), called RIO (remote I/O). RIO provides the most efficient type of data transfer. Make sure that your channel extenders are capable of supporting RIO. Contact HP Technical Support for more information.

If an update copy operation fails, the remote system suspends the affected pair or all Continuous Access Synchronous pairs in the journal. This is dependent on the type of failure. The suspended

14 Continuous Access Journal overview

pair or journal returns to Paired status when the primary and secondary storage systems are re-synchronized.

Read and Write I/O operations during remote copy operation

The primary system reads from the P-VOL when it receives a read I/O. If the read fails, the redundancy provided by RAID-1 or RAID-5 technology recovers the failure. The primary system does not read the S-VOL for recovery.

When a primary system receives a write I/O for a P-VOL in PAIR status, the system performs the update copy operation, as well as writing to the P-VOL. The write operation completes independently of the update copy operations on the S-VOL.

The secondary system updates the S-VOL according to the write sequence number in the journal data. This maintains data consistency between P-VOL and S-VOL.

If the P-VOL write operation fails, the primary system reports a unit check and does not create the journal data for this operation. If the update copy operation fails, the secondary system suspends either the affected pair or all Continuous Access Journal pairs in the journal, depending on the type of failure. When the suspended pair or journal is resumed, the primary and secondary systems negotiate the resynchronization of the pair(s).

During normal Continuous Access Journal operations, the secondary system does not allow S-VOLs to be online (mounted). Therefore, hosts cannot read from or write to S-VOLs. The S-VOL write enable option allows write access to a secondary data volume while the pair is split. The option is only available when you split the pair from the primary system.

To reduce the overhead associated with these remote copy activities and maximize data transfer, the P9500 storage system utilizes a special write command, which is allowed only for Continuous Access Journal initial and update copy operations. This command transfers the control parameters and the FBA format data for consecutive updated records in a track using a single write operation. The special Continuous Access Journal write command eliminates the overhead required for performing FBA to CKD and CKD to FBA conversions.

Remember that the host cannot write data to the Continuous Access Journal P-VOL belonging to the journal that was registered when 2DC Cascade is set to Enable in the Edit Journal Volume dialog box.

S-VOL write option

When a pair is split, you can set an option that will allow write I/O to the S-VOL. The S-VOL write option is selected during the Suspend Pair operation When performing the operation from the primary system. When you resynchronize a split pair whose S-VOL is write-enabled, the secondary system sends the S-VOL track bitmap to the primary system, which merges the P-VOL and S-VOL bitmaps to determine which tracks are out of sync. This ensures proper resynchronization of the pair.

Difference management

Differential data (updates during split or suspension) between the P-VOL and S-VOL is stored in a track bitmap. When a split/suspended pair is resumed, the primary system merges the P-VOL and S-VOL bitmaps, and the differential data is copied to the S-VOL.

The number of bitmap areas affects the maximum possible number of pairs that can be created in the storage system.

Pair status

Every pair operation results in a change in pair status. You should monitor pair status to insure that an operation completed successfully. Also, pairs must have a specific status in order for specific operations to be executed.

Read and Write I/O operations during remote copy operation 15

The following provides a brief description of the pair statuses. For complete details, see “Pair status

definitions” (page 67) .

• SMPL: A volume that is not assigned to a pair is in Simplex status, SMPL.

• COPY: When copy processing is started, the primary system changes the status of the P-VOL

and S-VOL to COPY.

• PAIR: When the initial copy processing is complete, the primary system changes the status of

both data volumes to PAIR.

• PSUE: When a pair is suspended due to an error condition, the primary system changes the

P-VOL and S-VOL status to PSUE (if the path status is normal).

• PSUS:

◦ When a pair is split by the user (pairsplit-r), the primary or secondary system changes

the status of the P-VOL and S-VOL to PSUS (if the path status is normal).

◦ If a pair is split from the secondary system, it changes the S-VOL status to PSUS. The

primary system detects the split (if path status is normal) and changes the P-VOL status to PSUS.

16 Continuous Access Journal overview

2 Requirements and specifications

This chapter provides system requirements for Continuous Access Journal.

System requirements

Continuous Access Journal operations are performed between the host(s) and the primary and secondary storage systems containing the P-VOLs and S-VOLs, using the data path.

General requirements for the Continuous Access Journal components are listed below.

Table 1 General system requirements

RequirementItem

Two—one at the local site, one at the remote site. Also, any combination of the following can be used with Continuous Access Journal:

Number of P9500 systems

• Four on primary side

• Four on secondary side

Continuous Access Journal

• Must be installed on primary and secondary P9500 storage systems.

• License keys required.

• On secondary systems, Continuous Access Journal can coexist with Continuous

Access Journal Z.

• When a virtual volume of Thin Provisioning (V-VOL) is used for a Continuous

Access Journal P-VOL or S-VOL, the capacity of the allocated pages for the V-VOL is included in the licensed capacity of Continuous Access Journal. If the actual licensed capacity exceeds the available licensed capacity, you may use Continuous Access Journal for 30 days. After 30 days, Continuous Access Journal pairs may only be split or released.

Other licenses required

• Continuous Access Synchronous is required, whether or not Continuous Access

Journal shares volumes with Continuous Access Synchronous).

• Continuous Access Journal 3DC & 4x4 Open MF in the following Continuous

Access Journal configurations:

- When running a 3DC system

- When performing Continuous Access Journal operations on multiple primary and secondary storage systems

The following program products can be used:

• Remote Web Console

Administrator or Continuous Access Journal write access is required; otherwise read access is provided with Remote Web Console.

• RAID Manager

Interfaces

UNIX based and PC-server platforms:Supported host platforms

• HP-UX 11.0 and 11i

• Oracle Solaris 9

• Windows 2000

• Windows 2003

• IBM AIX 5.1

Contact HP Technical Support for the latest information.

Fibre channel.Data path

System requirements 17

Table 1 General system requirements (continued)

RequirementItem

Volumes

• P-VOL and S-VOL must be equal in size.

• P-VOL and S-VOL must be of same emulation type.

• The maximum volume size of P-VOL and S-VOL is 4,194,304.000MB

(8,589,934,592Block). However, when XP12000 Disk Array or XP10000 Disk Array is used as the primary or secondary storage system, the maximum volume size is 2,949,120.00MB (6,039,797,760Block).

• The minimum volume size of P-VOL and S-VOL is 48.000MB (96,000Block).

• One Continuous Access Journal P-VOL may be copied to one S-VOL only.

• When Continuous Access Synchronous is cascaded with Continuous Access

Journal, a data volume may be copied to multiple data centers.

Limited per P9500 system. See “Maximum number of pairs allowed ” (page 25).Maximum number of pairs

Continuous Access Journal operations between P9500 and previous models are supported.

Supported previous models

See “Planning for previous models ” (page 31)

RAID1, RAID5, RAID6 are supported for the data volumes and journal volumes. RAID1, RAID5, and RAID6 can coexist in the same journal.

Supported RAID groups

Virtual LUN volume is supported.Supported volumes

• Can be used for data and journal volumes.

• S-VOL capacity must equal P-VOL capacity.

Cache Residency volume is supported as follows:

• Data volume: yes

• Journal volume: no

LUN Expansion volume is supported.

Must be operable for primary and secondary systems to insure pair creation success. The remote system cache should be configured to adequately support Continuous

Cache and Nonvolatile Storage (NVS)

Access Journal remote-copy workloads, as well as local workload activity. In general, cache capacity should be increased 25 percent for Continuous Access Journal. Also, an additional GB should be added for each journal on the system.

Required for disaster recovery.Host failover software

18 Requirements and specifications

Table 1 General system requirements (continued)

RequirementItem

RAID Manager consistency groups when multiple primary and secondary storage system

• Up to four journals can be registered in one RAID Manager consistency group.

If there are four storage systems, you must create one journal for each storage system.

• Up to 8,192 pairs, the total number of pairs registered in the journals in one

RAID Manager consistency group can be registered. However, it is recommended that you register only up to 4,096 pairs.

Journals

• Max. number: 256 (0 to 255) per storage system

• Recommended number: Up to 16

• Max. number of journal volumes: 64 per journal

• Max. number of data volumes: 8,192 per journal

• Journal numbers of master and restore journals that are paired can be different.

• A data volume and associated journal volume can belong to only one journal.

• Data volumes and journal volumes that belong to different controllers cannot

be in the same journal.

• The number of journal volumes in the master journal does not have to be equal

to the number of volumes in the restore journal.

• The P-VOLs and S-VOLs in a journal must be located in one physical primary

system and one physical secondary system (1-to-1 requirement).

• Each pair relationship in a journal is called a "Mirror". Each pair is assigned

a Mirror ID. Max. number of Mirror IDs = 4 (0 to 3).

• When Continuous Access Journal co-exists with Continuous Access Journal Z

in the same storage system, individual journals must be dedicated either to one or the other, but not both.

• Master and restore journals are managed according to the journal number.

NOTE: The capacity of journal volume is not included in the accounting capacity.

NOTE: Continuous Access Journal can co-exist with Continuous Access Journal Z in the same

storage system.

System requirements 19

3 Planning volumes and systems

This chapter provides information and instructions for planning Continuous Access Journal volumes, P9500 systems, and other important requirements and restrictions.

Plan and design workflow

Planning the Continuous Access Journal system is tied to your organization’s business requirements and production system workload. This means defining business requirements for disaster downtime and measuring the amount of changed data your system produces over time. With this information, you can calculate the size that journal volumes must be and the amount of bandwidth required to transfer update data over the data path network.

The plan and design workflow consists of the following:

• Assess your organization’s business requirements to determine recovery requirements.

• Measure your host application’s write-workload in MB per second and write-input/output per

second (IOPS) to begin matching actual data loads with the future Continuous Access Journal system.

• Use collected data along with your organization’s recovery point objective (RPO) to size

Continuous Access Journal journal volumes. Journal volumes must have enough capacity to hold accumulating data over extended periods.

The sizing of journal volumes can be influenced by the amount of bandwidth you settle on. Both efforts are interrelated. You may actually adjust journal volume size in conjunction with bandwidth to fit the organization’s needs.

• Use IOPS to determine data transfer speed into and out of the journal volumes. Data transfer

speed is determined by the number of Fibre Channel ports you assign to Continuous Access Journal, and by RAID group configuration. You need to know port transfer capacity and the number of ports that your workload data will require.

• Use collected workload data to size bandwidth for the fibre channel data path. As mentioned,

bandwidth and journal volume sizing, along with data transfer speed, are interrelated. Bandwidth may be adjusted in conjunction with the journal volume capacity and data transfer speed you plan to implement.

• Design the data path network configuration. This involves understanding supported

configurations, the need for fibre channel switches, the number of ports your data transfer requirements call for.

• Plan data volumes (primary and secondary volumes). This involves understanding the sizing

of P-VOL and S-VOL, RAID group considerations, and so on.

• Understand operating system requirements for data and journal volumes.

• Adjust cache memory capacity for Continuous Access Journal.

Some tasks will be handled by HP personnel. The planning information you need to address is provided in the following sections.

Assessing business requirements for data recovery

In a Continuous Access Journal system, when the data path continues to transfer changed data to the remote site, journals remain fairly empty. However, if a path failure or a prolonged spike in write-data that is greater than bandwidth occurs, data is stored in the journal. Changed data that is no longer moving to the remote system builds up in the master journal.

20 Planning volumes and systems

To ensure that journals can hold the amount of data that could accumulate, they must be sized according to the following:

• The maximum amount of time that journals could accumulate data. You develop this information

by determining your operation’s recovery point objective (RPO).

• The amount of changed data that your application generates. This is done by measuring

write-workload.

Determining your RPO

Your operation’s recovery point is the maximum time that can pass after a failure or disaster occurs before data loss is greater than the operation can survive.

For example, if the operation can survive one hour’s worth of lost data, and a disaster occurs at 10:00 am, then the system must be corrected by 11 a.m.

In regards to journal sizing, the journal must have the capacity to hold the data that could accumulated in one hour. If RPO is 4 hours, then the journal must be sized to hold 4-hours' worth of accumulating data.

To assess RPO, the host application’s write-workload must be known. With write-workload and IOPS, you or your organization’s decision-makers can analyze the number

of transactions write-workload represents, determine the number of transactions the operation could loose and still remain viable, determine the amount of time required to recover lost data from log files or key it in, and so on. The result is your RPO.

Write-workload

Write-workload is the amount of data that changes in your production system in MB per second. As you will see, write-workload varies. according to the time of day, week, month, quarter. That is why workload is measured over an extended period.

With the measurement data, you can calculate workload averages, locate peak workload, and calculate peak rolling averages, which show an elevated average. With one of these base data you will calculate the amount of data that accumulates over your RPO time, for example, 2 hours. This will be a base capacity for your journal volumes or represent a base amount of bandwidth your system requires.

Whether you select average, rolling average, or peak workload is based on the amount of bandwidth you will provide the data path (which is also determined by write-workload). Bandwidth and journal volume capacity work together and depend on your strategy for protecting data.

Measuring write-workload

Workload data is collected using Performance Monitor or your operating system’s performance-monitoring feature. The number of read/write transactions, or input/output per second (IOPS), is also collected by the software. You will use IOPS to set up a proper data transfer speed, which you insure through RAID group configuration and by establishing the number of Fibre Channel ports your Continuous Access Journal system requires. Each RAID group has a maximum transaction throughput; the ports and their microprocessors have an IOPS threshold.

Workload and IOPS collection is best performed during the busiest time of month, quarter, and year. This helps you to collect data that shows your system’s actual workloads during high peaks and spikes, when more data is changing, and when the demands on the system are greatest. Collecting data over these periods insures that the Continuous Access Journal design you develop will support your system in all workload levels.

Write-workload 21

To measure write-workload and IOPS

1. Using your performance monitoring software, collect the following:

• Disk-write bytes-per-second (MB/s) for every physical volume that will be replicated.

• Data should be collected over a 3 or 4-week period to cover a normal, full business cycle.

• Data should be collected at 5 minute intervals. If you use averages, shorter intervals

provide more accuracy.

2. At the end of the collection period, convert the data to MB/second, if needed, and import into a spreadsheet tool.

Sizing journal volumes

Determining the required journal volume capacity

The following factors determine the required journal volume capacity:

• The period of time during which data transfer can occur between hosts and the primary storage

system when there is a temporary increase in transferred data or a communication path fails between the primary storage system and secondary storage system.

• The data transfer speed for the period of time noted above.

To determine the journal volume capacity, use the following formula: Formula 1: Journal volume capacity > (V

H-M

- V

M-R

) × t

where:

• V

H-M

is the data transfer speed between hosts and the primary storage system.

• V

M-R

is the data transfer speed between the primary storage system and secondary storage

system.

• t is the length of time during which data transfer can occur.

To calculate the journal volume capacity required when a communication path fails between the primary storage system and secondary storage system, specify zero (0) for V

M-R

. The total capacity of journal volumes in each journal group must exceed the value in formula 1. When data in the primary data volume of the Continuous Access Journal delta resync pair is

updated, if the journal data that exceeds 70% of the journal volume capacity on the primary site of the Continuous Access Journal delta resync pair, the delta resync operation will fail. Therefore, specify the larger value for the journal volume capacity on the primary site of the Continuous Access Journal delta resync pair by comparing the values of formula 1 and formula 2.

Formula 2: Journal volume capacity > (V × t) × 1.5 where:

• V is the data transfer speed between a host and the primary storage system.

• t is the length of time until the delta resync operation starts.

CAUTION: The recommended journal volume capacity is 6 GB or more. If the capacity is less

than 6 GB, system performance may decrease due to the following:

• The new data cannot be stored because the journal volume is full.

• The performance of the initial copy decreases because the journal volume is full.

• The journal group is suspended because the journal volume is full.

• The indication of Usage Monitor is invalid.

22 Planning volumes and systems

Calculating the journal size

You calculate the size of journal volumes using write-workload and RPO.

To calculate the journal size

• Follow the instructions in (page 21).

• Use your system's peak write-workload and your organization's RPO to calculate the journal

size. For example:

RPO = 2 hours

Write-workload = 30 MB/sec

Calculate write-workload for the RPO. In the example, write-workload over a two-hour period is calculated as follows:

30 MB/second × 60 seconds = 1800 MB/minute

1800 MB/minute × 60 minutes = 108,000 MB/hour

108000 MB/hour × 2 = 416,000 MB/2 hours

Basic journal volume size = 416,000 MB (416 GB)

Journal volume capacity and bandwidth size work together. Your strategy for protecting data may allow you to adjust the bandwidth or the size of journal volumes. For a discussion on sizing strategies, see (page 35).

NOTE: If you are planning for disaster recovery, the remote array must be large enough to handle

the production workload, and therefore must be the same size as master journals. If you are not planning for disaster recovery, remote journal volumes may be smaller than master journal volumes.

Planning journals

Continuous Access Journal manages pair operations for data consistency through the use of journals. Continuous Access Journal journals enable update sequence consistency to be maintained across a group of volumes.

Understanding the consistency requirements for an application (or group of applications) and their volumes will indicate how to structure journals.

For example, databases are typically implemented in two sections. The bulk of the data is resident in a central data store, while incoming transactions are written to logs that are subsequently applied to the data store.

If the log volume “gets ahead” of the data store, it is possible that transactions could be lost at recovery time. Therefore, to insure a valid recovery image on a replication volume, it is important that both the data store and logs are I/O consistent by placing them in the same journal.

To plan journals, see the following:

• Review journal specifications in “System requirements” (page 17).

• Review journal configuration in “Register journal volumes in a journal ” (page 50).

Data transfer speed considerations

The previous sections and the sections later in this chapter on Bandwidth discuss the amount of data that must be stored temporarily in journals and transferred over the data path network. This section discusses the speed that data must be transferred in order to maintain the Continuous Access Journal system your are designing.

Data transfer speed considerations 23

The ability of your Continuous Access Journal system to transfer data in a timely manner depends directly on the following two factors:

• RAID group configuration

• Fibre Channel port configuration

Both of these elements must be planned to be able to handle the amount of data and number of transactions your system will move under extreme conditions.

RAID group configuration

A RAID group can consist of physical volumes with a different number of revolutions, physical volumes of different capacities, and physical volumes of different RAID configurations (for example, RAID-1 and RAID-5). The data transfer speed of RAID groups is affected by physical volumes and RAID configurations.

• The data transfer speed of a journal volume depends on the data transfer speed of the RAID

group to which it belongs. A RAID group can consist of one or more volumes, including journal volumes.

• Journal volumes must be configured in RAID groups according to the group’s throughput

specification and your system’s peak write-workload. If write-workload exceeds the RAID group’s throughput rating, then the number of RAID groups must be increased.

• Frequent read/write activity to non-journal volumes in a RAID group results in fewer read/writes

by journal volumes in the same RAID group. This can cause a drop in the data transfer speed of journal volumes. To avoid this, place journal volumes and frequently accessed non-journal volumes in different RAID groups.

Fibre Channel port configuration

The Fibre Channel ports on the P9500 have an IOPS threshold. Use the performance monitoring information for the number of IOPS your production system generates to calculate the number of Fibre Channel ports the Continuous Access Journal system requires.

Please see “Planning ports for data transfer ” (page 39) for a full discussion on the type and number of Fibre Channel ports required for your system.

Planning journal volumes

The following information is provided to help you prepare journal volumes:

• Identify the journal volumes for your Continuous Access Journal system on primary and

secondary arrays. Journal volumes should be sized according to RPO and write-workload. See “Sizing journal volumes ” (page 22) for more information.

• Journal volumes in the same journal can be of different capacity. A master journal volume

and the corresponding restore journal volume can be of different capacity.

• Journal volumes consist of two areas: one area is used for storing journal data, and the other

area is used for storing metadata.

• Journal volumes support all RAID configurations that are supported by P9500. Journal volumes

also support all physical volumes that are supported by P9500.

• Customized volumes can be used for journal volumes.

See system requirements and specifications in “Requirements and specifications” (page 17) for more information.

24 Planning volumes and systems

Planning pair volumes

The following information is provided to help you prepare volumes for configuration. Also, see system requirements and specifications in “Requirements and specifications” (page 17) for more information.

• The emulation and capacity for the S-VOL must be the same as the P-VOL

• When the S-VOL is connected to the same host as the P-VOL, the S-VOL must be defined to

remain offline.

• Continuous Access Journal supports the LUN Expansion feature, which allows you to configure

a LUSE volume by using 2 to 36 sequential LDEVs. If two LUSE volumes are assigned to a Continuous Access Journal pair, the capacity and configuration of the Continuous Access Journal S-VOL must be the same as the Continuous Access Journal P-VOL. For example, when the P-VOL is a LUSE volume in which 1-GB, 2-GB, 3-GB volumes are combined in this order, the S-VOL must be a LUSE volume in which 1-GB, 2-GB, 3-GB volumes are combined in this order. In addition, RAID1, RAID5, and RAID6 can coexist in the LUSE volume.

• Continuous Access Journal supports the Virtual LUN feature, which allows you to configure

custom-size LUs that are smaller than standard-size LUs. When custom-size LUs are assigned to a Continuous Access Journal pair, the S-VOL must have the same capacity as the P-VOL. For details about Virtual LUN feature, see HP P9000 Provisioning for Open Systems User Guide.

• Identify the volumes that will become the P-VOLs and S-VOLs. Note the port, group ID (GID),

and LUN of each volume. This information is used during the initial copy operation.

• You can create multiple pairs at the same time. For details, see (page 53).

• When you create a Continuous Access Journal pair, you will have the option to create only

the relationship, without copying data from primary to secondary volumes. You can use this option only when the contents of the primary and secondary data volume are completely the same.

Maximum number of pairs allowed

P9500 has a limit on the number of pairs that can be created. Therefore, it is necessary to calculate the maximum number of pairs on the P9500 storage system. The maximum number is limited according to the following:

1. The number of cylinders in the volumes, which must be calculated.

2. The number of bitmap areas required for Continuous Access Journal data and journal volumes. This is calculated using the number of cylinders.

3. The maximum number of pairs that can be created, calculated using the number of required bitmap areas.

CAUTION: The bitmap areas that are used for Continuous Access Journal are also used for

Continuous Access Journal Z, Continuous Access Synchronous Z, and Continuous Access Synchronous. If you use Continuous Access Journal with Continuous Access Journal Z, Continuous Access Synchronous Z, and Continuous Access Synchronous, use the total number of each pair’s bitmap areas to calculate the maximum number of pairs. In addition, if Continuous Access Journal and Continuous Access Synchronous share the same volume, use the total number of both pairs as well, no matter if the shared volume is primary or secondary.

Calculating maximum number of pairs

NOTE: In the calculations below, ceil() indicate that the value between the parentheses should

be rounded up to the nearest integer.

Planning pair volumes 25

To determine the number of cylinders

Use the following formula:

The number of cylinders = (ceil ( (ceil (Max. LBA/512) ) /15) ) + 1

where LBA = Logical Block Address

To calculate the number of required bitmap areas

Use the following formula

Required number of bitmap areas = (ceil((number of cylinders x 15) 122,752) )

where: “number of cylinders x 15” indicates the number of slots 122,752 = the number of slots that a bitmap area can manage

NOTE: If using LUSE volumes, add 1 to the required number of bitmap areas calculated in the

formula above.

To calculate the maximum number of pairs that can be created

The maximum number of pairs you can create is defined by the following:

• The number of LDEVs in the storage system

Table 2 The relationship between installed additional shared memory and the total number of LDEVs in the storage system

Total number of LDEVs in storage systemInstalled additional shared memory for Cnt Ac-J

16,384Base(16KLDEV,SI/VM)

65,28064KLDEV,SI/VM Extension1,FCV2,DP,Snapshot,TPF

• The number of bitmap areas required to create pairs (determined above)

• The number of bitmap areas of the storage system is 65,536.

Use the following formulae to calculate the maximum possible number of pairs that can be created, on the basis of the number of bitmap areas and the required number of bitmap areas you calculated:

Maximum number of pairs = floor( Number of bitmap areas / required number of bitmap areas )

If the calculated maximum number of pairs exceeds the total number of LDEVs of the storage system and the total LDEV number is less than 32,768, the total number of LDEVs in the storage system is the maximum number of pairs that can be created.

The maximum number of pairs is limited to 32,768.

Priority set for initial copy operations and scheduling order

For performing more initial copy operations than the setting value of the Maximum Initial Copy Activities set on the System Option dialog box, the scheduling order (Priority) can be set for the initial copy operations to be performed. This section explains the assignment of the scheduling order of initial copy operations in cases where two sets of multiple initial copy operations are performed.

An example is described in which 4 data volume pairs are created at the same time in cases where the setting value of the Maximum Initial Copy Activities is 2. The Priority which is set for the P-VOLs of data volume pairs is shown in the following table.

26 Planning volumes and systems

Table 3 Priority set for P-VOLs for which initial copy operation is performed

Value set for PriorityP-VOL

2LUN 00

3LUN 01

1LUN 02

4LUN 03

The order of starting initial copy and the Priority which is set for the P-VOLs are shown in the following table.

Table 4 Correspondence relationship between order of starting initial copy and priority set for P-VOLs

Value set for PriorityP-VOLOrder of starting initial copy

1LUN 021

2LUN 002

3LUN 013

4LUN 034

In this case, as the setting value of the Maximum Initial Copy Activities is 2, initial copy operations for LUN 02 and LUN 00 are started. If either one of the initial copy operations for LUN 02 and LUN 00 is completed, the initial copy for LUN 01 is started.

The next example explains the assignment of the scheduling order of initial copy operations in cases where initial copy is already performed and two volume pairs are newly added. The P-VOLs of the data volume pairs to be newly added and the Priority are shown in the following table.

Table 5 Priority set for P-VOLs of data volume pairs to be added

Value set for PriorityP-VOL

2LUN 10

1LUN 11

If initial copy is already started and if any initial copy is newly added, the additional initial copy is started after the previously performed initial copy is completed. The Priority of all the initial copy operations being performed is shown in the following table.

Table 6 Order of starting initial copy being performed

RemarkValue set for PriorityP-VOLOrder of starting initial copy

Data volume pair for which initial copy is already instructed to be performed

1LUN 021

Data volume pair for which initial copy is already instructed to be performed

2LUN 002

Data volume pair for which initial copy is already instructed to be performed

3LUN 013

Data volume pair for which initial copy is already instructed to be performed

4LUN 034

Planning pair volumes 27

Table 6 Order of starting initial copy being performed (continued)

RemarkValue set for PriorityP-VOLOrder of starting initial copy

Data volume pair for which initial copy is newly instructed to be performed

1LUN 115

Data volume pair for which initial copy is newly instructed to be performed

2LUN 106

Priority is determined within the range of the number of initial copy operations performed at the same time. Therefore, until the first initial copy operations complying with the order of the Priority are completed, the additional initial copy operations are not started.

Disaster recovery considerations

You begin a disaster recovery solution when planning the Continuous Access Journal system. The following are the main tasks for preparing for disaster recovery:

• Identify the data volumes that you wand to back up for disaster recovery.

• Pair the important volumes using Continuous Access Journal.

• Establish file and database recovery procedures.

• Install and configure host failover software error reporting communications (ERC) between the

primary and secondary sites.

For more information on host failover error reporting, see the following section. Also, review

“Disaster recovery operations ” (page 92) to become familiar with disaster recovery processes.

Host failover software

Host failover software is a critical component of any disaster recovery effort. When a primary storage system fails to maintain synchronization of a Continuous Access Journal pair, the primary storage system generates sense information. This information must be transferred to the remote site using the host failover software for effective disaster recovery. RAID Manager provides failover commands that interface with industry-standard failover products.

Sharing volumes with Continuous Access Synchronous, other program products

Continuous Access Journal volumes can be shared with other program product volumes. Sharing pair volumes results in enhanced replication solutions, for example when Continuous Access Journal and Continuous Access Synchronous, Business Copy, or External Storage Access Manager volumes are shared.

For planning information, see the following:

• “Continuous Access Journal configurations with Continuous Access Synchronous” (page 130)

• “Continuous Access Journal configurations with Business Copy” (page 143)

• “Continuous Access Journal configurations with External Storage Access Manager” (page 147)

• “Sharing Continuous Access Journal volumes ” (page 125) for the following program products:

LUN Expansion◦ ◦ Virtual LUN ◦ Cache Residency ◦ LUN Manager ◦ Thin Provisioning

28 Planning volumes and systems

◦ Data Retention ◦ Performance Monitor

Planning for Continuous Access Journal with multiple P9500 systems

A Continuous Access Journal system can be configured with up to four primary P9500 systems and four secondary P9500 system. Any combination of primary and secondary systems, from one to four, may be used. Figure 4 (page 29) shows an example configuration with multiple primary and secondary systems.

Figure 4 Using Continuous Access Journal with multiple storage systems

When primary hosts write data to P-VOLs, the hosts add a time stamp to the data. Secondary systems check time stamps and then restore data to data volumes in chronological order (older data are restored earlier), so that data update sequence is maintained.

Please note the following when working with multiple systems:

• Remote Web Console computers must be installed at primary and secondary sites.

• RAID Manager should be installed on the host in both the primary and secondary sites.

• Journal data is updated in the secondary systems based on the same time stamps and sequence

numbers issued by RAID Manager when the host issues the write requests to the primary system(s). Time and sequence information remains with the data as it moves to the master and restore journals and then to the secondary volume.

• Disaster recovery operations are possible. See “Disaster recovery when the system consists

of multiple primary and secondary storage systems” (page 94).

• If an error occurs in a journal, it is possible that all journals may become suspended by the

error. See “Suspension among journals ” (page 121) for more information.

Multiple journals per RAID Manager consistency group

Normally, only one journal can be registered in a RAID Manager consistency group. With multiple P9500 systems, however, up to four journals may be registered in a RAID Manager consistency group in the configuration of Figure 4 (page 29).

Planning for Continuous Access Journal with multiple P9500 systems 29

Figure 5 (page 30), Figure 6 (page 30), and Figure 7 (page 31) show varying configurations of

storage systems in which multiple journals are registered in a single RAID Manager consistency group.

Figure 5 RAID Manager consistency group with multiple journals—1

Figure 6 RAID Manager consistency group with multiple journals—2

30 Planning volumes and systems

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