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HP XP Racks User Manual

HP XP P9000 External Storage Access Manager User Guide

Abstract
This manual provides instructions and information for setting up, using, and maintaining External Storage Access Manager on the P9500 storage systems.
HP Part Number: AV400-96607 Published: January 2014 Edition: Eighth
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
Intel®, Itanium®, Pentium®, Intel Inside®, and the Intel Inside logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries
in the United States and other countries.
Microsoft®, Windows®, Windows® XP, and Windows NT® are U.S. registered trademarks of Microsoft Corporation.
Adobe® and Acrobat® are trademarks of Adobe Systems Incorporated.
Oracle is a registered US trademark of Oracle Corporation, Redwood City, California.
UNIX® is a registered trademark of The Open Group.
Export Requirements
You may not export or re-export this document or any copy or adaptation in violation of export laws or regulations.
Without limiting the foregoing, this document may not be exported, re-exported, transferred or downloaded to or within (or to a national resident of) countries under U.S. economic embargo, including Cuba, Iran, North Korea, Sudan, and Syria. This list is subject to change.
This document may not be exported, re-exported, transferred, or downloaded to persons or entities listed on the U.S. Department of Commerce Denied Persons List, Entity List of proliferation concern or on any U.S. Treasury Department Designated Nationals exclusion list, or to parties directly or indirectly involved in the development or production of nuclear, chemical, biological weapons, or in missile technology programs as specified in the U.S. Export Administration Regulations (15 CFR 744).
Warranty
WARRANTY STATEMENT: To obtain a copy of the warranty for this product, see the warranty information website:
http://www.hp.com/go/storagewarranty
Revision History
DescriptionDateEdition
Applies to microcode version 70-02-01-00/00 or later.May 2011First
Applies to microcode version 70-02-5x-00/00 or later.September 2011Second
Applies to microcode version 70-03-00-00/00 or later.November 2011Third
Applies to microcode version 70-03-30-00/00 or later.April 2012Fourth
Applies to microcode version 70-03-30-00/00 or later.August 2012Fifth
Applies to microcode version 70-03-30-00/00 or later.November 2012Sixth
Applies to microcode version 70-06-00-00/00 or later.July 2013Seventh
Applies to microcode version 70-06-11-00/00 or later.January 2014Eighth

Contents

1 External Storage Access Manager overview...................................................7
How ESAM works.....................................................................................................................7
ESAM components....................................................................................................................8
P9500 storage systems.........................................................................................................8
Main and remote control units...............................................................................................9
Pair volumes........................................................................................................................9
Data paths..........................................................................................................................9
Quorum disk.......................................................................................................................9
Multipath software ..............................................................................................................9
Remote Web Console GUI..................................................................................................10
RAID Manager (RAID Manager)..........................................................................................10
Data replication.....................................................................................................................10
Failover ................................................................................................................................10
2 System implementation planning and system requirements .............................11
The workflow for planning External Storage Access Manager implementation.................................11
Required hardware ................................................................................................................11
Multipath software .................................................................................................................12
Storage system requirements ...................................................................................................12
Licenses ................................................................................................................................12
License capacity ....................................................................................................................12
Pair volume requirements ........................................................................................................13
Quorum disk requirements ......................................................................................................14
Data path requirements and recommendations...........................................................................14
Remote Web Console requirements...........................................................................................15
External storage systems .........................................................................................................15
Planning failover.....................................................................................................................16
Preventing unnecessary failover................................................................................................17
Sharing volumes with other HP software products........................................................................17
Cache Partition .................................................................................................................18
Cache Residency...............................................................................................................19
Performance Monitor .........................................................................................................19
LUN Manager...................................................................................................................19
Open Volume Management................................................................................................19
LUN Expansion .................................................................................................................19
Configurations with Business Copy volumes ..........................................................................19
Configuring ESAM with Business Copy.............................................................................19
Configurations with Continuous Access Journal volumes .........................................................20
Configuring ESAM with Continuous Access Journal............................................................20
3 System configuration.................................................................................21
The basic workflow for configuring the system configuration.........................................................21
Connecting the hardware components.......................................................................................21
Prerequisites......................................................................................................................22
The workflow for connecting the hardware components...........................................................22
Installing and configuring software............................................................................................22
Additional documentation...................................................................................................23
Prerequisites......................................................................................................................23
The workflow for installing and configuring External Storage Access Manager...........................23
Configuring the primary and secondary storage systems..............................................................23
Additional documentation...................................................................................................23
Prerequisites......................................................................................................................24
Contents 3
Workflow..........................................................................................................................24
Configuring the quorum disks...................................................................................................24
Prerequisites......................................................................................................................24
Procedure.........................................................................................................................24
Adding the ID for the quorum disk to the storage systems.............................................................25
Prerequisites......................................................................................................................25
Procedure.........................................................................................................................25
Configuring host mode options.................................................................................................26
Prerequisites......................................................................................................................26
Procedure.........................................................................................................................26
4 Working with volume pairs........................................................................27
Workflow for ESAM volume pairs.............................................................................................27
Reasons for checking pair status...............................................................................................27
When to check pair status?......................................................................................................27
How pair status reflects system events and use............................................................................27
What pairs information can you view and where is it?.................................................................28
Where to find the information..............................................................................................29
How hosts see volume pairs.....................................................................................................29
Checking pair status ..............................................................................................................29
Pair status values....................................................................................................................30
Split types (PSUS status)......................................................................................................32
Suspend types (PSUE status)................................................................................................32
Volume pair creation ..............................................................................................................33
Creating an ESAM pair .....................................................................................................33
Prerequisites.................................................................................................................33
Procedure....................................................................................................................33
To verify host recognition of the ESAM P-VOL and S-VOL..............................................................35
How multipath software shows storage serial number for pairs......................................................36
Splitting pairs ........................................................................................................................36
Prerequisites......................................................................................................................36
Procedure.........................................................................................................................36
Resynchronizing pairs.............................................................................................................37
Reverse resynchronization....................................................................................................38
Prerequisites.................................................................................................................38
Procedure....................................................................................................................38
Releasing a pair.....................................................................................................................38
Changing Continuous Access Synchronous pairs to ESAM pairs ...................................................39
Requirements.....................................................................................................................40
Procedure.........................................................................................................................40
Comparison of the RAID Manager commands and Remote Web Console......................................41
5 System maintenance.................................................................................43
Applications used to perform maintenance tasks.........................................................................43
Required Remote Web Console settings................................................................................43
Related documentation............................................................................................................43
The different types of maintenance tasks....................................................................................43
Switching paths using multipath software .............................................................................43
Discontinuing ESAM operations ..........................................................................................43
Quorum disk ID deletion ....................................................................................................44
Deleting quorum disk IDs (standard method).....................................................................44
Deleting quorum disk IDs by system attribute (forced deletion).............................................45
Recovery of accidently deleted quorum disks.........................................................................45
Recovering the disk when the P-VOL was receiving host I/O at deletion................................45
Recovering the disk when the S-VOL was receiving host I/O at deletion................................46
Planned outages for system components................................................................................46
4 Contents
Options for performing the planned outages.....................................................................46
The procedures for performing planned outages................................................................47
Performing planned outages (quorum disk only) ...............................................................47
Performing planned outages (primary storage system and quorum disk)................................48
Performing planned outages (secondary storage system and quorum disk)............................49
Performing planned outages (both storage systems and quorum disk)...................................50
6 Disaster recovery......................................................................................51
Main types of failures that can disrupt your system......................................................................51
The basic recovery process......................................................................................................51
System failure messages..........................................................................................................51
Detecting failures....................................................................................................................51
Option 1: Check for failover first..........................................................................................51
Using Remote Web Console to check for failover...............................................................52
Using RAID Manager to check for failover........................................................................52
Using multipath software to check for failover....................................................................52
Option 2: Check for failures only.........................................................................................52
Determining which basic recovery procedures to use...................................................................53
Selecting Procedures..........................................................................................................53
Recovery from blocked pair volumes.........................................................................................54
Recovering from primary volume failure on the MCU..............................................................54
Recovering from secondary volume failure on the MCU...........................................................55
Recovering from primary volume failure on the RCU...............................................................56
Recovering from secondary volume failure on the RCU ...........................................................57
Recovery from quorum disk failure............................................................................................57
Replacement of quorum disks..............................................................................................57
Replacing a quorum disk when the MCU is receiving host I/O............................................57
Replacing a quorum disk when the RCU is receiving host I/O.............................................58
Recovery from power failure.....................................................................................................59
primary storage system recovery..........................................................................................59
Recovering the system when the RCU is receiving host I/O updates......................................59
Recovering the system when host I/O updates have stopped...............................................60
Secondary system recovery.................................................................................................61
Recovering the system when the P-VOL is receiving host updates..........................................61
Recovering the system when host updates have stopped.....................................................61
Recovery from failures using resynchronization............................................................................62
Required conditions............................................................................................................62
Determining which resynchronization recovery procedure to use...............................................62
Prerequisites.................................................................................................................63
Procedure....................................................................................................................64
Recovering primary volume from Business Copy secondary volume...........................................64
Prerequisites.................................................................................................................64
Procedure....................................................................................................................64
Recovering secondary volume from Continuous Access Journal primary volume .........................64
Prerequisites.................................................................................................................65
Procedure....................................................................................................................65
Postrequisites.....................................................................................................................65
Recovering from path failures ..................................................................................................65
Allowing host I/O to an out-of-date S-VOL.................................................................................66
Recovery for pairs shared by multiple hosts with VMware.............................................................66
7 Using ESAM in a cluster system..................................................................68
Cluster system architecture.......................................................................................................68
Required software...................................................................................................................68
Supported cluster software.......................................................................................................68
Configuration requirements .....................................................................................................69
Contents 5
Configuring the system............................................................................................................69
Disaster recovery in a cluster system..........................................................................................69
Restrictions ............................................................................................................................70
8 Troubleshooting........................................................................................71
Potential causes of errors ........................................................................................................71
Is there an error messages for every type of failure? ...................................................................71
Where do you look for error messages?....................................................................................71
Basic types of troubleshooting procedures..................................................................................71
Troubleshooting general errors ................................................................................................71
Suspended volume pair troubleshooting ....................................................................................73
The workflow for troubleshooting suspended pairs when using Remote Web Console..................73
Troubleshooting suspended pairs when using RAID Manager .................................................74
Location of the RAID Manager operation log file...............................................................74
Example log file............................................................................................................74
Related topics...............................................................................................................76
Recovery of data stored only in cache memory...........................................................................76
Pinned track recovery procedures.........................................................................................76
Recovering pinned tracks from volume pair drives...................................................................76
Recovering pinned tracks from quorum disks .........................................................................76
9 Support and other resources......................................................................77
Contacting HP........................................................................................................................77
Subscription service............................................................................................................77
Documentation feedback....................................................................................................77
Related information.................................................................................................................77
HP websites......................................................................................................................78
Conventions for storage capacity values....................................................................................78
Typographic conventions.........................................................................................................78
Rack stability..........................................................................................................................79
A Conventions............................................................................................80
Business Copy and Snapshot volumes.......................................................................................80
B ESAM GUI reference.................................................................................81
Pair Operation window...........................................................................................................81
Possible VOL Access values for pairs....................................................................................83
Detailed Information dialog box...........................................................................................84
Paircreate(ESAM) dialog box...............................................................................................86
Pairsplit-r dialog box..........................................................................................................88
Pairresync dialog box.........................................................................................................88
Pairsplit-S dialog box..........................................................................................................89
Quorum Disk Operation window .............................................................................................90
Add Quorum Disk ID dialog box.........................................................................................91
Glossary....................................................................................................93
Index.........................................................................................................95
6 Contents

1 External Storage Access Manager overview

ESAM ensures high availability of host applications used in P9500 (P9500) storage systems. ESAM provides protection against the loss of application availability when input and output (I/O) failures occur in the primary storage system by automatically switching host applications from the primary storage system to the secondary storage system and by enabling recovery from the failures that caused the I/O failure.
ESAM is designed for recovery from on-site disasters such as power supply failure. Continuous Access Synchronous is suited to large-scale disaster recovery.

How ESAM works

ESAM uses Continuous Access Synchronous software to create a synchronous remote copy of a production volume. But where Continuous Access Synchronous is suited to large-scale disaster recovery, ESAM is intended for recovery from on-sight disasters such as power supply failure.
Because of this, ESAM is configured differently than a typical Continuous Access Synchronous configuration.
• The ESAM primary and secondary storage systems are connected to the same host. When
an ESAM pair is created, the host sees the primary and secondary volumes as the same volume.
• ESAM requires multipath software to be installed on the host. In the event that the host cannot
access the production volume on the primary storage system, host I/O is redirected via the host multipath software to the secondary volume on the remote system. Failover is accomplished without stopping and restarting the application.
• ESAM is used on open host systems only.
• An ESAM pair consists of a primary data volume (P-VOL) on the primary storage system and
a secondary data volume (S-VOL) on the secondary storage system (like Continuous Access Synchronous). The S-VOL is the copy of the P-VOL.
• ESAM uses a quorum disk located on an external storage system, which keeps track of
consistency between the P-VOL and S-VOL. Consistency data is used in the event of an unexpected outage of the data path or primary storage system. In this case, the differential data in both systems is compared and, if the pairs are consistent, host operations continue on the secondary storage system.
How ESAM works 7

ESAM components

A typical configuration consists of two P9500 storage systems installed at the primary and secondary sites. In addition, the ESAM system consists of the following components:
• ESAM and Continuous Access Synchronous software, which are installed on both systems.
• A host server running a multipath software solution, qualified with ESAM software, that is
connected to both storage systems.
• Dedicated Fibre Channel data paths linking the primary and secondary storage systems, with
Fibre Channel switches.
• A qualified external storage system to host the quorum disks. This storage system must be
accessible to both the primary and secondary storage systems.
• The following interface tools for configuring and operating the pairs:
Remote Web Console (RWC) graphical user interface (GUI), located on a management
◦
LAN.
◦ RAID Manager (RAID Manager), located on the host.
ESAM components are illustrated in the following figure and described in more detail in the following topics.

P9500 storage systems

ESAM operations are conducted between P9500 (P9500) and another storage system on the primary and secondary sites. The primary storage system consists of the main control unit (MCU) and service processor (SVP). The secondary storage system consists of the remote control unit (RCU) and SVP.
The primary storage system communicates with the secondary storage system over dedicated Fibre Channel remote copy connections.
8 External Storage Access Manager overview

Main and remote control units

Like Continuous Access Synchronous, ESAM replication relationships exist at the Logical Control Unit (LCU) level within the storage systems.
• Primary storage system LCUs containing the production volumes to be replicated are called
MCUs (main control units).
• Secondary storage system LCUs containing the copy volumes are called remote control units
(RCUs). Normally the MCU contains the P-VOLs and the RCU contains the S-VOLs. The MCU communicates with the RCU via the data path. You can simultaneously set P-VOL and
S-VOL in the same storage system if the volumes are used by different pairs. In this case, the CU can function simultaneously as an MCU for the P-VOL and as an RCU for the S-VOL.
The MCU is often referred to as the primary storage system in this document; the RCU is often referred to as the secondary storage system.

Pair volumes

Original data from the host is stored in the P-VOL; the remote copy is stored in the S-VOL. Data is copied as it is written to the P-VOL; new updates are copied only when the previous updates are acknowledged in both primary and secondary volumes.
Once a pair is created, you can do the following:
• Split the pair, which suspends copy activity.
• Resynchronize the pair, which restores and maintains synchronization.
• Delete the pair, which removes the pair relationship, though not the data.

Data paths

The physical links between the primary and secondary storage systems are referred to as the "data path." These links include the Fibre Channel interface cables and switches. ESAM commands and data are transmitted through the data path. The data path links the primary and secondary storage systems through two types of Fibre Channel ports, Initiator and RCU Target ports.
Because paths are one-directional, and ESAM communicates in both directions, a minimum of two data paths are needed; however, HP requires a minimum of two in each direction for greater support and security of the data. A maximum of eight data paths in each direction are supported. Therefore, the maximum number of logical paths between any two storage systems is sixteen (eight forward and eight reverse).

Quorum disk

The quorum disk is a continuously updated volume that contains information about the state of data consistency between the P-VOL and S-VOL. The information is used by ESAM in the event of failure to direct host operations to the secondary volume. The quorum disk is located in an externally attached storage system.

Multipath software

Multipath software distributes the loads among the paths to the current production volume. For ESAM, the multipath software duplicates the paths between the host and P-VOL, so that the paths are in place between the host and the S-VOL also.
If a failure occurs in the data path to the primary storage system, or with the primary storage system, the multipath software transfers host operations to the S-VOL in the secondary storage system.
ESAM components 9

Remote Web Console GUI

You perform ESAM tasks using the RWC graphical user interface. RWC is installed on a management computer. It communicates with the SVP of each storage system over defined TCP/IP connections.

RAID Manager (RAID Manager)

You can run commands using RAID Manager to perform pair tasks, which is installed on the host. You run commands from a command device on the host. Disaster recovery operations use a mix of RWC and RAID Manager.

Data replication

ESAM supports data sharing between the following volumes:
• A volume in the primary P9500 system and a volume in secondary P9500 system.
• Volumes in external storage systems.
• A volume in the primary or secondary storage system and a volume in an external storage
system.

Failover

A failover is an automatic takeover of operations from the primary storage system to the secondary storage system. This occurs when the primary storage system cannot continue host operations due to a failure in either the data path or the primary storage system. The multipath software in the host switches I/O to the remote system. A multipath software package that has been qualified with ESAM must be installed on the host.
10 External Storage Access Manager overview

2 System implementation planning and system requirements

Understanding the system planning process and the various requirements of ESAM enables you to plan a system that functions properly and can be configured to meet your business needs over time.

The workflow for planning External Storage Access Manager implementation

The process for planning your ESAM implementation involves these two main tasks:
• Plan and configure the volume pairs, data path configurations, bandwidth sizing, RAID
configuration.
For more information, see the HP XP P9000 Continuous Access Synchronous User Guide.
• Follow all of the ESAM requirements and recommendations.
There are major differences between ESAM and Continuous Access Synchronous. For example,
use of the quorum disk and multipath software on the host are specific to ESAM.
NOTE: HP strongly recommends that you contact Global Solutions Services for assistance in the
planning and configuration of your HP system.

Required hardware

The following hardware is required for an ESAM system:
• Storage systems must be installed on the primary and secondary sites.
• ESAM pairs can be set up between the following HP systems. Note the required microcode
versions.
◦ Two P9500s, on the primary and secondary sites (70-01-62-XX/XX or later)
◦ A P9500 (70-03-0X-XX/XX or later) and XP24000 (60-05-0x or later). Either storage
system can be on the primary or secondary site.
• A host must be connected to both primary and secondary storage systems.
• An external storage system for the quorum disk.
• External storage system for data storage (optional).
• Data path connections between primary and secondary storage systems.
• A physical path connection between the primary storage system and the external system
hosting the quorum disk.
• A physical path connection between the secondary storage system and the external system
hosting the quorum disk.
• Path connections from host to primary and secondary storage systems. Multipath software
must be installed on each host server for this purpose.
• If necessary, physical path connections between external storage and primary and/or
secondary storage systems.
The workflow for planning External Storage Access Manager implementation 11

Multipath software

A multipath software package qualified with ESAM is required on each host platform for failover support. Hitachi's multipath software, Dynamic Link Manager, supports the following host platforms:
• AIX
• Linux
• Solaris
• Windows. Requires host mode option 57 on the host group where Windows resides.
• VMware. Requires host mode option 57 on the host group where VMware resides.
Dynamic Link Manager manages I/O through a disk driver.For version information, contact your HP representative.

Storage system requirements

The requirements for the primary, secondary, and external storage systems must be met to ensure these systems function properly.
• Make sure that the primary, secondary, and external storage systems have their own
independent sources of power.
• The ESAM P-VOL and S-VOL must be located in different storage systems.
• Primary and secondary storage systems each require two initiator ports and two RCU target
ports.
• If you use switches, prepare them for both the primary and the secondary storage systems.
• Secondary storage system cache should be configured to support remote copy workloads, as
• Cache and non-volatile storage (NVS) must be operable for both the MCU and RCU. If not,
• The required program products for ESAM operations must be installed.

Licenses

The following HP software products must be installed on both the primary and secondary storage systems. Each product each requires a license key.
◦ The initiator port sends ESAM commands to the paired storage system. Initiator ports must
be configured on the primary storage system for ESAM operations. However, for disaster recovery, you should also configure initiator ports on the secondary storage system.
◦ RCU Target port receives ESAM commands and data. RCU target ports must be configured
on the secondary storage system for ESAM operations. You should also configure RCU target ports on the secondary storage system for disaster recovery.
Additional microprocessors for replication links may be required based on replication workload.
Do not share a switch between the two. Using two independent switches provides redundancy in the event of failure in one.
well as any local workload activity.
the ESAM Paircreate RAID Manager command will fail.
• External Storage Access Manager
• Continuous Access Synchronous
• External Storage

License capacity

A single ESAM license must be purchased for each P9500 system. The ESAM license is not capacity based. The capacity of the Continuous Access Synchronous license determines the capacity of
12 System implementation planning and system requirements
ESAM volumes that may be replicated. Review the Continuous Access Synchronous license installed on your system to verify that it meets your requirements.
For example, when the license capacity for Continuous Access Synchronous is 10GB, the volume capacity that can be used for ESAM is up to 10GB. When 2GB out of 10GB of license capacity for Continuous Access Synchronous is used, the volume capacity that can be used for ESAM is up to the remaining 8GB.
For information on licenses and the actions to take for expired licenses and exceeded capacity, see the HP XP P9000 Remote Web Console User Guide.

Pair volume requirements

Data in the P-VOL on the primary storage system is copied to the S-VOL on the secondary storage system. These two volumes are a pair.
The following are requirements for setting up P-VOLs and S-VOLs:
• LDEVs for the P-VOL and S-VOL must be created and formatted before creating a pair.
• The volumes must have identical block counts and capacity.
• A P-VOL can be copied to only one S-VOL; and an S-VOL can be the copy of only one P-VOL.
• Maximum number of pairs per storage system is 65,536.
The number of ESAM pairs that can be created depends on whether Continuous Access
Synchronous and/or Continuous Access Journal are used in the same storage system. ESAM,
Continuous Access Synchronous, and Continuous Access Journal share the same bitmap areas
used to manage differential data, which affects number of pairs. If one or both of these products
are used, the maximum number of the ESAM pairs allowed is than 65,536 and must be
calculated.
For instructions, see the topic on difference management in the HP XP P9000 Continuous
Access Synchronous User Guide.
• The emulation type for P-VOLs and S-VOLs is OPEN-3, OPEN-8, OPEN-9, OPEN-E, OPEN-L,
and OPEN-V.
• Multiple LU paths to each volume must be set using LUN Manager.
For instructions, see the HP XP P9000 Provisioning for Open Systems User Guide.
• If you are storing data in an external volume or volumes, make sure the external volumes are
mapped to the primary or secondary storage system they support.
• If you plan to create multiple pairs during the initial copy operation, observe the following:
All P-VOLs must be in the same primary storage system, or in mapped external systems.◦
◦ All S-VOLs must be in the same secondary storage system, or in mapped external systems.
◦ You can specify the number of pairs to be created concurrently during initial copy
operations (1 to 16). For more information about the System Option dialog box, see the topic on changing
option settings in the HP XP P9000 Continuous Access Synchronous User Guide.
◦ During the initial pair operation in RWC, you will select multiple P-VOLs on the primary
storage system for pairing. After selecting the P-VOL, only the P-VOL with the lowest LUN appears in the subsequent Paircreate dialog box. To pair the other P-VOLs to the correct S-VOLs, observe the following:
- In the Paircreate dialog box, you can select only one S-VOL. This should be the volume to be paired with the P-VOL that is shown.
- S-VOLs for the remaining P-VOLs are assigned automatically by RWC, according to their LUNs. If you are creating three P-VOLs, and you assign LUN001 as the S-VOL in the
Pair volume requirements 13
Paircreate dialog box, the remaining S-VOLs will be assigned incrementally by LUN (for example, LUN002 and LUN003).
- Make sure that all S-VOLs to be assigned automatically are available, are numbered in an order that will pair them properly, and that they correspond in size to the P-VOLs.
- If an S-VOL is not available for a P-VOL, the pair must be created individually.

Quorum disk requirements

Quorum disks store continually-updated information about data in ESAM P-VOLs and S-VOLs for use during failover operations.
• All ESAM pairs created between one MCU and one RCU must use the same quorum disk.
Thus, The P-VOL and S-VOL for a pair must use the same quorum disk.
• A quorum disk must be located in an external storage system that is separate from the primary
and secondary storage systems.
• Only external storage systems supported by External Storage can be used for the quorum
disk. see the HP XP P9000 External Storage for Open and Mainframe Systems User Guide for a list of supported external systems.
NOTE: If the ESAM pair is created between P9500 and XP24000, the quorum disk must
be located in an external storage system supported by XP24000. For a list of supported storage systems, see the HP XP 24000 External Storage User’s Guide.
• Multiple quorum disks can be created in one external storage system.
• The maximum number of quorum disks per external system is 128.
• The external system is not required to be dedicated to quorum disks exclusively.
• Quorum disk size requirements: 47 MB to 4 TB (96,000 blocks to 8,589,934,592 blocks).
• The quorum disk must not be expanded or divided by LUN Expansion or Hitachi Virtual
LVI/LUN.
• An LU path must not be configured to the quorum disk.
• Read/Write operations from the storage system to the quorum disk are for internal use. These
operations are performed even when Write Pending operations reach 70%.
CAUTION: Quorum disks are used in a unique way in that they are shared with two storage
systems. For data protection reasons, make sure not to share any other kind of volume with two storage systems.

Data path requirements and recommendations

Data is transmitted from the P-VOL to the S-VOL over the data path. Please observe the following requirements and recommendations:
• Data path requirements for ESAM are the same as Continuous Access Synchronous
requirements. For more information, see the HP XP P9000 Continuous Access Synchronous User Guide.
• Do not share the data paths with Continuous Access Synchronous. Install independent data
paths for ESAM.
• Install at least two data paths from the primary storage system to the secondary storage system,
and two data paths from the secondary storage system to the primary storage system. This allows data transfer to continue in the event of failure one path's cables or switches.
• Optical fibre cables are required to connect the primary and secondary storage system.
14 System implementation planning and system requirements
• Direct and switch connections are supported.
• Use target ports in the primary and secondary storage systems to connect with the host Fibre
Channel ports.
Initiator ports cannot be used for host connections.
For more information about port attributes, see the topic on configuring host interface ports
in the HP XP P9000 Continuous Access Synchronous User Guide.
• The following table shows maximum, minimum, and recommended number of data paths,
logical paths, and ports for ESAM.
RecommendedMax.Min.ItemCategory
Physical Data Paths
Ports
host.
quorum disk.
system and quorum disk).
connected to an initiator port.
system target port.

Remote Web Console requirements

The following requirements must be met to ensure that you are able to use RWC to manage the system:
• RWC is required for ESAM.
2 or more41Path between primary/secondary systems and a
2 or more81Data path from primary to secondary system.
2 or more81Data path from secondary to primary system.
2 or more81Path between primary/secondary systems and
2 or more81From primary to secondary system.Logical Paths
2 or more81From secondary to primary system.
2 or more81Mapping path (path between primary/secondary
641Secondary system target port that can be
161Initiator port that can be connected to a secondary
• You can connect a RWC computer to both the primary and secondary storage system.
• You must have storage administrator authority to perform ESAM tasks. If you do not, you will
only be able to view ESAM information.
• To perform any ESAM task, make sure RWC is in Modify Mode.
For more information, see the HP XP P9000 Remote Web Console User Guide.

External storage systems

You can use HP storage systems, original equipment manufacturer (OEM) storage systems, and other vendors' storage systems (such as IBM or EMC) as connectable external storage systems. Hosts will recognize these volumes as internal volumes of the P9500 storage system.
Remote Web Console requirements 15
When using external storage systems with ESAM, please observe the following:
• Optional external storage systems may be used to store pair data.
For supported external systems, see the HP XP P9000 External Storage for Open and Mainframe Systems User Guide.
• You can connect one external system per ESAM P-VOL, and one per S-VOL.
• The maximum number of external systems that can be connected depends on the number of
the external ports that can be defined for a storage system.

Planning failover

Automatic failover of host operations to the secondary storage system is part of the ESAM system. Failover occurs when the primary storage system cannot continue I/O operations due to a failure. The multipath software in the host switches I/O to the secondary storage system.
• The multipath software automatically configures the path to the P-VOL as the owner path when
you create an ESAM pair.
• The path to the S-VOL is automatically configured as the non-owner path.
In the ESAM system, the quorum disk stores the information about the state of data consistency between the P-VOL and S-VOL, which is used to check whether P-VOL or S-VOL contains the latest data. If the P-VOL and S-VOL are not synchronized due to a failure, the MCU and RCU determine which volume should accept host I/O based on the information stored in the quorum disk.
The following figure illustrates failover when a failure occurs at the MCU.
ESAM also performs the following checks to detect failures:
• The RCU issues service information messages (SIMs) when the data path is blocked. The
multipath software issues messages about the failure in the host-MCU paths.
• Health check of the quorum disk by the MCU and RCU. The primary or secondary storage
system issues a SIM if a failure in the quorum disk is detected. Host operations will not switch to the S-VOL if the quorum disk fails. In this case, the failure must be cleared as soon as possible and the quorum disk recovered.
• If the multipath software detects a failure in the host-to-pair volume paths, the operation switches
to a different available path and no SIM is issued. To stay informed about path status, monitor the path failure messages issued by the multipath software.
• The multipath software issues message when all host-MCU paths fail. These messages must
then be checked and the cause corrected. If failover took place, host operations should be switched back to the primary storage system.
16 System implementation planning and system requirements
It is possible that maintenance operations require both storage systems to be powered off at the same time. In this case, the health checking periods would be shortened to prevent unexpected failover while both systems are powered off.
After failover, when a failure is corrected, you may continue operations on the S-VOL, though HP recommends switching them back to the P-VOL. To find which volume was originally a P-VOL, use the multipath software on the host to refer to path information, checking for the volume with the owner path. The owner path is set to the volume that you specified as a P-VOL when you created an ESAM pair. The owner path never switches even if the P-VOL and S-VOL were swapped due to a failover.

Preventing unnecessary failover

Some applications issue the read command to the ESAM S-VOL. When these applications are used, and when the number of read commands to the S-VOL reaches or exceeds the threshold (1,000 times per six minutes), ESAM assumes that a P-VOL failure has occurred. This situation results in an unnecessary failover to the ESAM S-VOL.
At this time, the Solaris VERITAS Volume Manager (VxVM) vxdisksetup command issues more read commands than allowed by the threshold.
You can prevent unnecessary failover by setting host mode option 48 to ON. Note that when this option is ON, the S-VOL responds slower to the read command.
Review system conditions and resulting behaviors related to host mode option 48 in the following table.
Table 1 System behavior for host mode option 48
Normal operation.
The S-VOL receives more read commands than allowed by the threshold, and receives no write command.
more write commands.
Failover occurs only when you run certain applications.
• Updates from a host go to S-VOL, and
S-VOL status becomes SSWS.
• •The S-VOL responds to the read
command as quickly as the P-VOL responds.
• Updates from a host go to S-VOL, and
S-VOL status becomes SSWS.
• The S-VOL responds to the read
command as quickly as the P-VOL responds.
For more information about setting host mode options, see the HP XP P9000 Provisioning for Open Systems User Guide.

Sharing volumes with other HP software products

ESAM volumes can be used as volumes for other HP software products, such as Business Copy or Virtual LUN.
The following table shows the ESAM volumes that can be shared with other software. Only those volumes listed can be shared.
Behavior when ONBehavior when OFFEvent
No failover, even when you run the applications.
• Updates from a host go to P-VOL, and
S-VOL status remains PAIR. The S-VOL responds slower to the read
command than the P-VOL does. The S-VOL takes several milliseconds to respond.
Same as when option 48 is OFF.The S-VOL receives one or
Preventing unnecessary failover 17
Table 2 Volume types that can be shared with ESAM volumes
Management
Used as ESAM S-VOL?Used as ESAM P-VOL?VolumesProduct
YesYesVolume where an LU path is definedLUN Manager
NoNoVolume where no LU path is defined
YesYesVolume where LUN security is applied
YesYesCustomized Volume volumeOpen Volume
NoNoSystem disk
YesYesLUSE volumeLUN Expansion
NoNoN/AVolume Shredder
YesYesTHP V-VOL (virtual volume)Thin Provisioning
NoNoPool volume
YesYesExternal volume (after mapping is finished)External Storage
YesNoBusiness Copy P-VOLBusiness Copy
NoNoBusiness Copy S-VOL
NoNoReserved volume
NoNoData volume, Virtual volume, Pool volumeFast Snap
NoNoData volume, virtual volume, pool volumeSnapshot
NoNoP-VOL, S-VOLContinuous Access
Synchronous
YesNoPrimary data volumeContinuous Access
Journal
NoNoSecondary data volume
NoNoJournal volume
NoNoSource volumeAuto LUN
NoNoTarget or reserved volume
YesYesVolume with the Read/Write attributeData Retention
NoNoVolume with attribute other than the above
NoNoN/ADatabase Validator
NoNoN/AMultiplatform Backup
The quorum disk cannot be used by other software products, except as follows:
• Cache Partition can allocate the CLPR (virtually partitioned cache) to the quorum disk when
you map the quorum disk to the storage system.
• Performance Monitor can monitor usage or performance of the quorum disk.
The following topics clarify key information regarding the use of other software products.

Cache Partition

Virtually partition the cache (CLPR), and allocate the CLPR to the host that issues the I/O to the ESAM pairs.
18 System implementation planning and system requirements

Cache Residency

With Cache Residency, you can improve data access performance by storing the ESAM data in the storage system's cache memory.

Performance Monitor

• Performance Monitor is used to monitor usage or performance of the storage system. You can
also show statistical I/O data of ESAM and Continuous Access Synchronous pairs.
• When Performance Monitor data collection results in a large amount of data, significant traffic
on the P9500 internal LAN can occur. To prevent time-outs while performing ESAM operations
on the RWC computer, cancel Performance Monitor data collection activities.

LUN Manager

LU paths cannot be deleted after you create ESAM pairs. To delete the LU path, you need to release the ESAM pair first.

Open Volume Management

• Customized Volume volumes can be assigned to ESAM pairs, provided that the S-VOL has
the same capacity as the P-VOL.
• To perform Customized Volume operations on an existing ESAM P-VOL or S-VOL, the pair
must be released first to return the volume to the SMPL status.

LUN Expansion

LUSE volumes can be assigned to ESAM pairs, provided that both P-VOL and S-VOL are LUSE volumes consisting of the same number of LDEVs, the same size, and the same structure.

Configurations with Business Copy volumes

You can use the ESAM S-VOL as a Business Copy P-VOL. This configuration benefits the ESAM pair if the P-VOL is logically destroyed. In this case, you can recover the data from the split Business Copy S-VOL.
Configuring ESAM with Business Copy
You perform this configuration by creating an ESAM pair, a Business Copy pair, then splitting the Business Copy pair.
1. Create the ESAM pair. Make sure that pair status becomes PAIR.
2. Create the Business Copy pair, using the ESAM S-VOL as a Business Copy P-VOL.
3. Split the Business Copy pair and resume host operations on the ESAM P-VOL.
Sharing volumes with other HP software products 19

Configurations with Continuous Access Journal volumes

You can use the ESAM S-VOL as a Continuous Access Journal (Cnt Ac-J) P-VOL. This configuration benefits the ESAM pair if data in the P-VOL and S-VOL become inconsistent due to a disaster. In this case, you can recover the data from the split Cnt Ac-J S-VOL.
Configuring ESAM with Continuous Access Journal
You perform this configuration by creating an ESAM pair and a Cnt Ac-J pair.
1. Create the ESAM pair. Make sure that the pair status becomes PAIR.
2. Create the Cnt Ac-J pair. Specify the ESAM S-VOL as a Cnt Ac-J P-VOL.
20 System implementation planning and system requirements

3 System configuration

The ESAM system configuration process is the first main task in the process of setting up the ESAM system. It follows the planning of the system implementation and is based on the outcome of the system implementation planning effort. All of the configuration procedures must be completed before you can begin using the system.

The basic workflow for configuring the system configuration

The configuration process involves connecting the system hardware components, installing all required software, configuring the primary and secondary storage systems, setting up the quorum disk, and configuring host mode options.
Complete the configuration tasks in the indicated order and configure the components according to the configuration requirements.
Use the following process to configure ESAM:
1. Connect the system hardware components.
For more information, see “Connecting the hardware components” (page 21).
2. Install the required software.
For more information, see “Installing and configuring software” (page 22).
3. Configure the primary and secondary storage systems (MCU and RCU).
“Configuring the primary and secondary storage systems” (page 23).
4. Set up a quorum disk.
For more information, see “Configuring the quorum disks” (page 24).
5. Add the quorum disk ID.
For more information, see “Adding the ID for the quorum disk to the storage systems” (page 25).
6. Configure host mode options.
For more information, see “Configuring host mode options” (page 26).

Connecting the hardware components

Connecting certain hardware components of the system is the first main task in the system configuration. Completion of this task ensures that the data paths required for normal system operation are set up and ready for use.
During this task, you and HP representatives connect the following system components:
• The host to the primary and secondary P9500 systems.
• The primary to the secondary storage system.
• The external system that has the quorum disk to the primary and secondary storage systems.
• Any optional external storage systems to the primary and/or secondary storage systems.
• Initiator ports (primary storage system) to the RCU Target ports (secondary storage system).
The basic workflow for configuring the system configuration 21

Prerequisites

Before you begin, make sure you have:
• Completed the system implementation (see “System implementation planning and system
requirements ” (page 11)).

The workflow for connecting the hardware components

Use the following process to connect the hardware components for a ESAM system:
1. If you have external storage for storing pair data, connect the external systems to the external
ports on the P9500 systems.
2. Connect the host to the primary and secondary storage systems using target ports on the
P9500 systems.
3. Make the connections for the data path between the primary and secondary storage systems
by doing the following:
• Connect the initiator ports on the primary storage system to the RCU Target ports on the secondary storage system.
• Connect the initiator ports on the secondary storage system to the RCU Target ports on the primary storage system.
4. Connect the quorum disk to the primary and secondary storage systems using external ports
on the P9500 systems.
CAUTION: For data protection reasons, make sure that quorum disks are not shared by two
storage systems.
The following figure shows these connections.

Installing and configuring software

Installing and configuring the system software is the second main task in the system configuration. Completion of this task ensures that all of the software required for normal system operation is installed and ready for use. This task involves installing multipath software and RAID Manager on the host and installing the main system software on the primary and secondary storage systems.
22 System configuration

Additional documentation

To ensure that you use the correct steps to install the software, refer to the installation instructions in the following documentation during the installation process:
• The documentation for the multipath software.
• The HP XP P9000 Remote Web Console User Guide.
• The HP XP P9000 RAID Manager Installation and Configuration User Guide.

Prerequisites

Before you begin, make sure you have:
• Connected the system hardware components (see “Connecting the hardware components”
(page 21)).
• The required software for ESAM is installed (see “System implementation planning and system
requirements ” (page 11)).
CAUTION: Make sure that you install the software in the order described in the procedure. If
you do not, you may have to uninstall and reinstall the software.

The workflow for installing and configuring External Storage Access Manager

Use the following process to install and configure ESAM and the required software:
1. Install multipath software on the host.
2. Using the multipath software, set the path health-checking period to three minutes.
3. Install the following required software on the primary and secondary storage systems using
RWC:
• External Storage Access Manager
• Continuous Access Synchronous
• External Storage
4. Install RAID Manager on the hosts.

Configuring the primary and secondary storage systems

Configuring the primary and secondary storage systems (MCU and RCU) is the third main task in the system configuration. Completion of this task ensures that the systems are configured to enable the communication and data transfer between the systems that is essential to normal system operation. Part of this task is setting up the logical paths between the systems.
This task involves setting port attributes You can set the number of pairs the system creates concurrently (at the same time) during this task This task involves installing multipath software and RAID Manager on the host and installing the main system software on the primary and secondary storage systems.

Additional documentation

To ensure that you use the correct steps to configure the systems, refer to these instructions in the following documentation during the configuration process:
• Setting the number of volumes to be copied concurrently in the HP XP P9000 Continuous
Access Synchronous User Guide.
• Defining port attributes in the HP XP P9000 Continuous Access Synchronous User Guide.
• Configuring storage systems and defining logical paths in the HP XP P9000 Continuous Access
Synchronous User Guide.
Configuring the primary and secondary storage systems 23
• Details about mapping the primary and secondary storage systems to the external system that
contains the in the HP XP P9000 Provisioning for Open Systems User Guide and HP XP P9000 External Storage for Open and Mainframe Systems User Guide.
• Details about CLPR in the HP XP P9000 Cache Partition User Guide.
• Details about external path groups in the HP XP P9000 External Storage for Open and
Mainframe Systems User Guide.

Prerequisites

Before you begin, make sure you have:
• Installed the multipath and system software (see “Installing and configuring software”
(page 22)).

Workflow

Use the following process to configure the primary and secondary storage systems:
1. Stop Performance Monitor, if it is running, to avoid performance impact on the TCP/IP network.
2. Set the port attributes for ESAM.
3. Configure the primary and secondary storage systems and establish logical paths between
the primary and secondary VSP systems.

Configuring the quorum disks

The quorum disk stores information about the data in the P-VOL and S-VOL. The quorum disk is used to determine which pair volume has the latest data when a failover is required.
Instructions in this topic describe the following:
• How to configure a quorum disk
• How to configure port parameters for the quorum disk on the primary and secondary systems

Prerequisites

• The quorum disk must be located in an external storage system that is separate from the primary
and secondary storage systems. For all requirements, see “Quorum disk requirements ”
(page 14).
• If MCU and RCU system configuration has changed, you must reformat the quorum disk volume
in the external storage system.
• Multipath and system software must be installed. See “Configuring the primary and secondary
storage systems” (page 23).

Procedure

1. In the external storage system, prepare a volume for use as the quorum disk and specify any required system options. See “Quorum disk requirements ” (page 14).
2. Using the External attribute, configure the ports on the primary and secondary storage systems that are connected to the disk.
3. Set the paths from the disk to the primary and secondary storage systems to Active.
4. Using RWC’s Ports/Host Groups and External Storages windows, map the primary and secondary storage systems to the disk by doing the following:
• Configure at least two cross-system paths between the primary storage system and quorum
disk, and two between the secondary storage system and the quorum disk.
• Specify the these external volume parameters:
- Emulation type: OPEN-V.
24 System configuration
- Number of LDEVs: 1.
- Cache mode: This parameter is not used for quorum disks. Either Enable or Disable can
be specified.
- Inflow control: Select Disable. Data will be written in the cache memory.
- CLPR: If you partition cache memory, specify the CLPR that the quorum disk uses.
- LDKC:CU:LDEV number: The number is used to identify the quorum disk for the primary and secondary storage systems.
5. In the External Path Groups tab in RWC, configure port parameters for the primary and
secondary storage systems by specifying the following values:
• QDepth: This is the number of Read/Write commands that can be issued (queued) to the
quorum disk at a time. The default is 8.
• I/O TOV: This is the timeout value to the quorum disk from the primary and secondary
storage systems. The value must be less than the time-over value from the application. Recommended: 15 seconds Default: 15 seconds
• Path Blockade Watch: This is the time that you want the system to wait after the quorum
disk paths are disconnected before the quorum disk is blocked. Recommended: 10 seconds; Default: 10 seconds.

Adding the ID for the quorum disk to the storage systems

Adding the ID for the quorum disk is the fourth main task in the system configuration. Completion of this task ensures that the primary and secondary storage systems to which the disk has been mapped can recognize the disk.

Prerequisites

Before you begin, make sure you have:
• Configured the quorum disk (see “Configuring the quorum disks” (page 24)).

Procedure

To ensure that the quorum disk ID is added correctly, make sure that:
• You complete the procedure on the primary and secondary storage systems.
• You use the same ID for the disk on both systems.
1. Delete any data in the external volume that you assigned to be the quorum disk.
2. Access the MCU or RCU in RWC, then click Actions > Remote Copy > Continuous Access Synchronous > Quorum Disk Operation.
3. Make sure that you are in the modify mode.
4. In the Quorum Disk Operation window, right-click the quorum disk ID that you want to add, then click Add Quorum Disk ID.
5. In Add Quorum Disk ID dialog box, from the Quorum Disk drop-down menu, select the LDKC:CU:LDEV number that you specified when mapping the external volume. This is the volume that will be used for the quorum disk.
6. From the RCU drop-down menu, select the CU that is to be paired with the CU on the current storage system. The list shows the RCU serial number, LDKC number, controller ID, and model name registered in CU Free.
7. Click Set. The settings are shown in the Preview area.
Adding the ID for the quorum disk to the storage systems 25
8. Verify your settings. To make a correction, select the setting, right-click, and click Modify.
9. Click Apply to save your changes.

Configuring host mode options

Configuring host mode options is the last main task in the system configuration. Completion of this task ensures that the host mode option setting are correct. The settings vary depending on the whether the system is a standard or cluster implementation.

Prerequisites

Before you begin, make sure you have:
• Added the ID for the quorum disk to the storage systems (see “Adding the ID for the quorum
disk to the storage systems” (page 25)).

Procedure

Use the following host mode options for your system:
• If using VMware or Windows, set host mode option 57 on the host group where VMware or
Windows reside.
• If using software that uses a SCSI-2 Reservation, set host mode option 52 on the host groups
where the executing node and standby node reside.
For more information on host mode options, see the HP XP P9000 Provisioning for Open Systems User Guide.
26 System configuration

4 Working with volume pairs

A number of tasks must be performed on volume pairs as part of your normal ESAM system maintenance activities, when troubleshooting system issues, or when taking action to recover from failure.

Workflow for ESAM volume pairs

You perform several different types of tasks with volume pairs as part of your system maintenance and recovery activities.
The different types of tasks include:
• Checking pair status.
• Creating pairs.
• Releasing pairs.
• Resynchronizing pairs.
• Splitting pairs.
All of the different pair-related tasks can be performed using RWC or RAID Manager.

Reasons for checking pair status

Pair status information indicates the current state or condition of the pair. There are two main reasons for checking the current status of a volume pair. One is to verify the
status of the pair while you run pair RAID Manager commands during normal system maintenance or failure recovery. The other reason is to check the status of pairs as part of your normal system monitoring activities to ensure they are working properly.

When to check pair status?

You should check the status of volume pairs whenever you run pair RAID Manager commands and as part of your normal system monitoring activities.
When you run pair RAID Manager commands, you check pair status:
• Before you run a pair RAID Manager command.
• During pair changes. Check pair status to see that the pairs are operating correctly and that
data is updating from P-VOLs to S-VOLs in PAIR status, or that differential data management is happening in Split status.
NOTE: You can perform a pair task can only be completed if the pair is in a status that permits
the task. Checking the status before you run a RAID Manager command lets you verify that the pair is in a status that permits the task.

How pair status reflects system events and use

The storage system records information about the current status of ESAM pairs. You can check the current status of any volume pair at any time.
Status changes occur for the following reasons:
• Automatic system events, such as errors or failover situations.
• Administrator actions, such as creating, releasing, or deleting pairs.
The following figure shows ESAM pair status before and after pair creation, splitting pairs, various errors, and after releasing a pair.
Workflow for ESAM volume pairs 27
1. When a volume is not in an ESAM pair, its status is SMPL.
2. When you create an ESAM pair using SMPL volumes, the status of the P-VOL and the S-VOL
changes to COPY while the system copies the data.
3. A stable synchronized pair has the status PAIR.
4. When you split a pair, the status of the P-VOL and the S-VOL changes to PSUS (pair
suspended-split, split by command).
5. When the MCU cannot maintain in synch the P-VOL and the S-VOL because of an error, the
status of the P-VOL and the S-VOL changes to PSUE (pair suspended-error, split due to an error). If the MCU cannot communicate with the RCU, the status of the S-VOL stays PAIR.
6. When a failover occurs in the storage system, the status of the S-VOL changes to SSWS, and
the status of the P-VOL changes to PSUS.
7. When you resynchronize the pair in PSUS or PSUE status (see No.4 and No.5), the status of
the P-VOL and the S-VOL changes to COPY.
8. When you resynchronize the pair with the S-VOL in SSWS status (see No.6), (using the RAID
Manager pairresync -swaps command on the S-VOL), the P-VOL and the S-VOL swap, and the pair status changes to COPY.
9. When you release a pair, the status of the P-VOL and the S-VOL changes to SMPL.

What pairs information can you view and where is it?

You can monitor the following information for pairs:
• Percentage of synchronization (Sync. column)
• Pair details (Detailed Information dialog box)
Pair status◦
◦ Split types
◦ Suspend types
28 Working with volume pairs

Where to find the information

You can view all information about pairs in the GUI. If you configured the system to send email notifications, you can monitor those particular events remotely.
When a pair is in PSUS, SSWS, or PSUE status, the primary storage system generates SIMs (service information messages). You can check SIMs in RWC’s Alerts window.

How hosts see volume pairs

When you create an ESAM pair, the host sees the primary and secondary volumes as the same volume.
The following figure shows:
• The configuration as seen by the host.
• The actual configuration with primary and secondary volumes.

Checking pair status

Use RWC to view the current status of volume pairs.
1. In the RWC main window, click Actions > Remote Copy > Continuous Access Synchronous > Pair Operation.
2. In the Pair Operation window tree, select the CU group, CU, port, or the host group where the ESAM pair belongs.
The list shows Continuous Access Synchronous and ESAM pairs.
3. You can complete the following tasks:
• To make sure data is current and review the status information in the Status column, click
File/Refresh.
• To filter the list to show only ESAM pairs, open the Display Filter window.
• To view pair status details, right-click the ESAM pair and click Detail.
You can complete the following tasks in the Detailed Information dialog box:
• See information about other volumes. Click Previous or Next.
• Edit the current information for the pair. Click Update.
• Close the dialog box. Select the Refresh the Pair Operation window after this dialog box
closes option to update the information in the Pair Operation window based on the updated information on the Detailed Information dialog box. Click Close.
How hosts see volume pairs 29
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