Hewlett Packard Enterprise HPE XP7 User Manual
HPE XP7 Fast Snap User Guide
Abstract
This guide provides information about how to configure and use Fast Snap to store snapshots
in an XP7 Storage system. This document is intended for system administrators and Hewlett
Packard Enterprise representatives and authorized service providers who install, configure,
and operate the XP7 Storage system.
Part Number: 858749-403
Published: January 2019
Edition: 18
©
Copyright 2018 Hewlett Packard Enterprise Development LP
The information contained herein is subject to change without notice. The only warranties for Hewlett Packard Enterprise 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. Hewlett Packard Enterprise shall not be liable for technical or editorial errors or
omissions contained herein.
Confidential computer software. Valid license from Hewlett Packard Enterprise 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.
Links to third-party websites take you outside the Hewlett Packard Enterprise website. Hewlett Packard Enterprise has no control
over and is not responsible for information outside the Hewlett Packard Enterprise website.
Acknowledgments
Microsoft® and Windows® are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other
countries.
Java® and Oracle® are registered trademarks of Oracle and/or its affiliates.
UNIX® is a registered trademark of The Open Group.
Contents
Overview of Fast Snap............................................................................8
About Fast Snap........................................................................................................................... 8
Workflow for storing Fast Snap snapshot data...................................................................8
Components of Fast Snap............................................................................................................ 9
Fast Snap pairs................................................................................................................ 11
Volume components.........................................................................................................12
Snapshot tree components ............................................................................................. 13
Maximum number of Fast Snap pairs.............................................................................. 13
Consistency and snapshot groups................................................................................... 13
Snapshot Clones .............................................................................................................14
Snapshot trees and cascaded pairs ................................................................................14
Creating cascaded pairs.................................................................................................. 15
Volume differences between Fast Snap and Business Copy...........................................17
XP7 Storage software applications for Fast Snap............................................................20
How Fast Snap works................................................................................................................. 21
How Fast Snap uses pools and pool volumes................................................................. 21
Usage level rebalancing among parity groups................................................................. 21
How Fast Snap uses V-VOLs...........................................................................................22
How Fast Snap pairs are created.....................................................................................22
Using snapshot pairs (not cascaded) ..............................................................................23
Using cascaded pairs.......................................................................................................23
Workflow for creating groups and storing snapshot data using RAID Manager...............26
Methods of storing snapshot data.................................................................................... 28
Fast Snap pair restoration................................................................................................29
How Fast Snap pair status changes........................................................................................... 29
Fast Snap host access and pair status............................................................................ 31
Workflow for Fast Snap pair status changes....................................................................31
Copy threshold option and host server I/O performance for Fast Snap......................................33
Sharing Fast Snap volumes with other software applications.....................................................33
Sharing Fast Snap volumes that have Data Retention access attributes........................ 35
Sharing Fast Snap volumes with Auto LUN..................................................................... 38
Sharing Fast Snap volumes with Business Copy.............................................................38
Sharing Fast Snap volumes with Continuous Access Synchronous and Continuous
Access Journal.................................................................................................................41
Sharing Fast Snap volumes with High Availability........................................................... 44
Sharing Fast Snap volumes with Thin Provisioning and Thin Provisioning MF in a
single storage system.......................................................................................................53
Sharing Fast Snap volumes with Resource Partition....................................................... 54
Acronyms and abbreviations for XP7 Storage system software applications used in this
guide........................................................................................................................................... 54
Fast Snap system and planning requirements.................................. 55
Fast Snap system requirements................................................................................................. 55
Fast Snap licensed capacity requirements...................................................................... 55
Fast Snap shared memory requirements.........................................................................56
Fast Snap volume requirements...................................................................................... 56
Fast Snap data pool requirements................................................................................... 60
Fast Snap consistency group requirements.....................................................................61
Fast Snap snapshot group requirements......................................................................... 63
Contents 3
Fast Snap planning requirements............................................................................................... 63
Calculating the number of Fast Snap pairs based on pair tables.....................................64
Calculating Fast Snap pairs based on the snapshot estimated manageable capacity.... 64
Calculating Fast Snap pairs based on cache management devices................................65
Calculating the number of cache management devices.................................................. 66
Calculating the Fast Snap pair capacity for THP pools....................................................66
Fast Snap cache management device requirements.......................................................68
Calculating and assigning pool capacity.......................................................................... 69
External Storage and external volumes used as pool-VOLs............................................71
Simultaneous processing of multiple Fast Snap pair tasks..............................................71
Pair operations when pairs are cascaded ....................................................................... 72
Pair operations when pairs are not cascaded.................................................................. 83
Pair operations when a P-VOL is shared by multiple S-VOLs......................................... 84
Data recovery and backup differences between Fast Snap and Business Copy.............85
Removing Fast Snap.................................................................................................................. 86
Configuring Fast Snap..........................................................................88
Prerequisites for configuring Fast Snap......................................................................................88
Workflow for configuring Fast Snap............................................................................................ 88
Workflow for creating and managing Fast Snap pairs......................................................89
Creating Fast Snap data pools.........................................................................................89
Selecting pool volumes.................................................................................................... 92
Pool creation and data drive type priority.........................................................................94
Workflow for registering virtual volumes..................................................................................... 95
Editing the SSID for virtual volumes ................................................................................95
Changing V-VOL settings.................................................................................................98
Creating V-VOLs for Fast Snap S-VOLs........................................................................100
Overview of using RAID Manager to run commands through in-band connections................. 108
Changing system options that affect Fast Snap performance.................................................. 108
Managing Fast Snap Pairs..................................................................112
Fast Snap pair tasks..................................................................................................................112
Checking Fast Snap pair status................................................................................................ 112
Reloading Fast Snap configuration information........................................................................ 112
Workflow for creating and managing Fast Snap pairs...............................................................113
Workflow for creating Fast Snap pairs using Remote Web Console.........................................113
Creating Fast Snap pairs using Remote Web Console.............................................................114
Selecting a pool as your primary volume........................................................................117
Example of creating complex Fast Snap pairs..........................................................................118
Pair operations for each consistency group.............................................................................. 119
Adding Fast Snap pairs to snapshot or consistency groups using RAID Manager........ 119
Workflow for defining Fast Snap pairs and defining them in snapshot or consistency
groups using Remote Web Console...............................................................................119
Storing snapshot data or cloning pairs........................................................................... 119
Splitting Fast Snap pairs to store snapshot data...................................................................... 120
Splitting Fast Snap pairs to store snapshot data using RAID Manager......................... 121
Workflow for storing snapshot data or clone pairs in consistency groups.................................121
Using consistency group pair-split with shared volumes................................................122
Restoring Fast Snap pairs........................................................................................................ 124
Failure during Fast Snap pair restore.............................................................................126
Restoring suspended Fast Snap pairs........................................................................... 126
Fast Snap pair resynchronization............................................................................................. 126
Pair resynchronization methods.....................................................................................126
Resynchronizing Fast Snap pairs.................................................................................. 127
4 Contents
Assigning MU numbers to deleted snapshot data.................................................................... 127
Deleting snapshot data............................................................................................................. 128
Deleting Fast Snap pairs...........................................................................................................129
Accelerating the Fast Snap pair deletion process..........................................................130
Removing Fast Snap snapshot groups.......................................................................... 130
Assigning secondary volumes to Fast Snap pair snapshot data.............................................. 131
Assigning secondary volumes to snapshot data after creating new Fast Snap pairs.... 131
Assigning secondary volumes to snapshot data of existing Fast Snap pairs.................132
Releasing assignment of secondary volumes from Fast Snap pair snapshot data.................. 133
Changing assignment of secondary volumes to Fast Snap pair snapshot data....................... 134
Monitoring and maintaining Fast Snap.............................................136
Monitoring pair information....................................................................................................... 136
Viewing summary replication information.......................................................................136
Viewing local replication summary information.............................................................. 137
Viewing the number of pairs...........................................................................................139
Viewing the list of primary volumes................................................................................139
Viewing pair properties ..................................................................................................140
Fast Snap pair status definitions.................................................................................... 141
Viewing pair synchronization rates.................................................................................142
Monitoring consistency groups................................................................................................. 143
Viewing the number of consistency groups....................................................................143
Viewing the list of consistency groups............................................................................145
Viewing consistency group properties............................................................................145
Viewing Fast Snap pair task history..........................................................................................147
Fast Snap task code definitions..................................................................................... 149
Viewing licensed capacities...................................................................................................... 150
Viewing the number of cache management devices.................................................................150
Managing pools.........................................................................................................................151
Monitoring pool information............................................................................................151
Viewing used pool capacity ...........................................................................................153
Viewing formatted pool capacity and pool usage rates..................................................154
Increasing pool capacity.................................................................................................155
Decreasing pool capacity............................................................................................... 159
Editing the data pool warning threshold......................................................................... 163
Editing pool names.........................................................................................................165
Workflow for recovering blocked pools...........................................................................168
Workflow for decreasing pool capacity...........................................................................170
Managing virtual volumes......................................................................................................... 172
Editing virtual volume names......................................................................................... 172
Workflow for deleting V-VOLs specified for Fast Snap S-VOLs..................................... 174
Viewing snapshot data capacity ...............................................................................................175
Maintaining pairs during storage system maintenance.............................................................176
Switching off the power supply.......................................................................................176
Definition of failure.................................................................................................................... 177
Troubleshooting Fast Snap................................................................178
Overview................................................................................................................................... 178
Failures in a cascaded configuration........................................................................................ 178
Troubleshooting the source of SIM codes.................................................................................179
Troubleshooting pools, pairs, and volumes related to Fast Snap............................................. 179
Workflow for correcting pool-related failures (SIM = 601xxx, 602xxx, 604xxx,
605xxx, and 606xxx)...................................................................................................... 184
Workflow for fixing errors when SIMs related to cache management devices are reported..... 190
Contents 5
Calculating the number of remaining cache management devices................................190
Workflow for fixing errors when pool-related SIMs are reported...............................................190
Completing SIMs ......................................................................................................................192
Automatic completion of SIMs........................................................................................192
Manually completing SIMs............................................................................................. 192
RAID Manager command reference for Fast Snap.......................... 194
Pair tasks using RAID Manager or Remote Web Console........................................................194
RAID Manager pair command results.......................................................................................195
Parameter ranges for RAID Manager options...........................................................................196
Troubleshooting with RAID Manager........................................................................................ 196
RAID Manager SSB2 codes...........................................................................................196
Notes on using Fast Snap primary volumes as Continuous Access Synchronous,
Business Copy, or Continuous Access Journal pair volumes........................................ 206
Fast Snap GUI windows and wizards................................................208
Replication window................................................................................................................... 208
Local Replication window..........................................................................................................211
View Pair Synchronization Rate window...................................................................................227
View Pair Properties window.....................................................................................................231
History window..........................................................................................................................238
Consistency Group Properties window..................................................................................... 240
Create FS Pairs wizard............................................................................................................. 244
Create FS Pairs window.................................................................................................244
Assign Secondary Volumes window.............................................................................. 253
Create FS Pairs confirmation window............................................................................ 260
Select Pool window...................................................................................................................267
Split Pairs wizard.......................................................................................................................269
Split Pairs window.......................................................................................................... 269
Split Pairs confirmation window..................................................................................... 272
Resync Pairs wizard..................................................................................................................274
Resync Pairs window..................................................................................................... 274
Resync Pairs confirmation window................................................................................ 277
Delete Pairs window................................................................................................................. 279
Edit Local Replica Options wizard............................................................................................ 281
Edit Local Replica Options window................................................................................ 281
Edit Local Replica Options confirmation window........................................................... 286
FS Pairs window....................................................................................................................... 287
Assign Secondary Volumes wizard...........................................................................................292
Assign Secondary Volumes window.............................................................................. 293
Assign Secondary Volumes confirmation window..........................................................299
Remove Secondary Volumes window.......................................................................................305
6 Contents
Websites.............................................................................................. 308
Support and other resources.............................................................309
Accessing Hewlett Packard Enterprise Support....................................................................... 309
Accessing updates....................................................................................................................309
Customer self repair..................................................................................................................310
Remote support........................................................................................................................ 310
Warranty information.................................................................................................................310
Regulatory information.............................................................................................................. 311
Documentation feedback...........................................................................................................311
Contents 7
Overview of Fast Snap
About Fast Snap
To store snapshot data, you create a pair with a logical volume functioning as the P-VOL, and a virtual
volume as the S-VOL. A pair created to store snapshot data is referred to as a snapshot pair. A snapshot
pair displays showing the snapshot attribute.
When you create a Fast Snap pair, the status changes to "PAIR" and snapshot data is stored. You can
use Fast Snap to store a maximum of 1,024 snapshots of data (including the number of clones when you
clone a volume).
Updating the P-VOL first copies the differential data as snapshot data in pool volumes (pool-VOL), and
then updates the data. Snapshot data is a copy of differential data in Fast Snap P-VOLs. If your storage
system experiences a data storage failure, you can restore the data using the snapshot data in the pool.
Splitting a Fast Snap pair saves a snapshot and stops the copying of replaced data in the pool.
The following figure provides a basic illustration of storing snapshot data.
You can use snapshot data in open-system volumes.
More information
How Fast Snap uses V-VOLs on page 22
Splitting Fast Snap pairs to store snapshot data on page 120
Workflow for storing Fast Snap snapshot data
1. Create a Fast Snap pair. You can create a pair with the snapshot attribute (snapshot pairs). The pair is
in "PAIR" status.
2. The host updates the primary volume.
3. Split the snapshot pairs. The snapshot data of the primary volume is stored (Snapshot data A in the
figure below).
8 Overview of Fast Snap
4. The host updates the primary volume again.
5. Split the snapshot pairs. The updated data in the primary volume is stored as snapshot data
(Snapshot data B in the following figure). In the event of data corruption, you can recover using this
snapshot data.
The following figure illustrates how data in the pool is replaced.
NOTE: Because Snapshot data A and Snapshot data B are handled as a Fast Snap S-VOL of a snapshot
pair, the host can reference the P-VOL, Snapshot data A, and Snapshot data B.
Components of Fast Snap
Fast Snap components:
• Fast Snap pairs (clone and snapshot pairs).
• Volume related components (P-VOL, S-VOL, and pools)
• Snapshot tree related components (root volume, node volumes, and leaf volumes)
Groups:
• Consistency groups
• Snapshot groups
Software applications for XP7 Storage systems:
• Fast Snap
• Thin Provisioning (THP)
• RAID Manager
Components of Fast Snap 9
You can run RAID Manager commands to perform Fast Snap tasks (see Pair tasks using RAID
Manager or Remote Web Console on page 194). When using RAID Manager, run commands
directly from the host instead of using a management client.
10 Overview of Fast Snap
Fast Snap pairs
Type Volume that can
be used as P-VOL
Pairs with the
snapshot attribute
Logical volume
(LDEV)
Volume that can
be used as S-VOL
Fast Snap V-VOL
(V-VOL of which
provisioning type is
Snapshot in RWC,
or V-VOL created
by the raidcom
add ldev -pool
snap command in
RAID Manager)
THP V-VOL Yes
Cascade
capability
No
Description
Pairs used to store
snapshot data.
The logical volume
of the P-VOL
contains THP VVOLs (V-VOL of
which provisioning
type is Thin
Provisioning in
RWC, or V-VOL
created by the
raidcom add
ldev -pool
command in RAID
Manager).
Pairs used to store
snapshot data. To
create a cascaded
pair with the
snapshot attribute,
use a THP V-VOL
as the S-VOL. To
use a THP V-VOL
as the S-VOL,
make sure to
specify a cascaded
pair (with the
cascade attribute
enabled)
regardless of
whether it is in a
cascaded
configuration.
Pairs with the clone
attribute
Logical volume
(LDEV)
THP V-VOL Yes
The logical volume
of the P-VOL
contains THP VVOLs (V-VOL of
which provisioning
type is Thin
Provisioning in
RWC, or V-VOL
created by the
raidcom add
ldev -pool
command in RAID
Manager).
Pairs to be cloned.
Fast Snap pairs 11
Type Volume that can
Volume components
Volume type Volumes that can be used Description
Primary Logical volume (LDEV) Logical volume of a P-VOL
be used as P-VOL
Volume that can
be used as S-VOL
Cascade
capability
contains THP V-VOLs (V-VOLs of
which provisioning type is Thin
Provisioning in RWC, or V-VOL
created by raidcom add ldev
-pool in RAID Manager).
Description
The logical volume
of the P-VOL
contains THP VVOLs (V-VOL of
which provisioning
type is Thin
Provisioning in
RWC, or V-VOL
created by the
raidcom add
ldev -pool
command in RAID
Manager).
Secondary Fast Snap V-VOL (V-VOL of
which provisioning type is
Snapshot in RWC, or V-VOL
created by raidcom add ldev
-pool snap in RAID Manager)
THP V-VOL
Pool Logical volume (LDEV) Volumes that configure a pool
Use this volume to create
snapshot pairs. Cannot be used
for cascaded or cloned pairs.
This volume is required to create
a pair with the S-VOL specified.
Use this volume to create
cascaded or cloned pairs.
This volume is required to create
a pair with the S-VOL specified.
Cloned pairs must be created
with the S-VOL specified.
When a THP V-VOL is used as
an S-VOL, you must specify a
cascaded or cloned pair.
which stores snapshot data.
Differential data of a P-VOL is
stored in a pool volume as
snapshot data.
12 Volume components
Snapshot tree components
Volume type Volumes that can be used Description
Root Logical volume (LDEV)
Node THP V-VOL
Leaf THP V-VOL
Volume (L1 pair of the P-VOL) in
the top layer of a snapshot tree.
The logical volume of the P-VOL
contains THP V-VOLs (V-VOL of
which provisioning type is Thin
Provisioning in RWC, or V-VOL
created by raidcom add ldev
-pool in RAID Manager).
Volumes located between the
root volume and leaf volumes.
S-VOL of the root volume (or
another node volume), and the PVOL of a leaf volume (or another
node volume).
Volumes in the bottom layer of a
snapshot tree.
S-VOL of the root volume or a
node volume, which is not a PVOL of any pair.
Maximum number of Fast Snap pairs
The maximum number of pairs that can be created on the XP7 storage system is 1,048,575.
Consistency and snapshot groups
A consistency group can include Fast Snap (FS), Business Copy (BC), and Business Copy MF (BC MF)
pairs. Use consistency groups to split the Fast Snap pairs that are defined in the group. Splitting the pairs
using the group assures data consistency at the time the XP7 Storage system receives the request.
A snapshot group is a group of only Fast Snap pairs. Use consistency or snapshot groups to perform Fast
Snap tasks on all of the pairs within the group. You define Fast Snap pairs to a snapshot group when you
create the pairs.
The following table shows the differences between consistency groups and snapshot groups.
Item Consistency group Snapshot group
Pair limit per group 8,192 8,192
Limit 2,048 2,048
Data consistency Guaranteed Not guaranteed
Software application from which you can define pairs FS, BC, and BC MF FS
For more information about defining Cnt Ac-S pairs in consistency groups, see the HPE XP7 Continuous
Access Synchronous User Guide.
Snapshot tree components 13
For more information about defining Cnt Ac-J pairs in consistency groups, see the HPE XP7 Continuous
Access Journal User Guide.
For more information about defining BC pairs in consistency groups, see the HPE XP7 Business Copy
User Guide.
More information
Workflow for creating groups and storing snapshot data using RAID Manager on page 26
Adding Fast Snap pairs to snapshot or consistency groups using RAID Manager on page 119
Removing Fast Snap snapshot groups on page 130
Pair tasks using RAID Manager or Remote Web Console on page 194
Snapshot Clones
When distributing data in a storage system, you can use clones to improve efficiency.
The following figure illustrates cloning.
When cloning pairs, use a logical volume as the P-VOL and a THP V-VOL as the S-VOL.
If you split pairs that have the clone attribute, the data of the entire P-VOL is copied to the S-VOL
asynchronously to create a clone of the primary volume. When the copy completes, pairs are deleted and
the S-VOL is unpaired (becomes a THP V-VOL). This volume can be used as a volume in the same
status as the P-VOL. This operation is referred to as cloning pairs.
A maximum of 1,024 clones (including the number of snapshots if you store them) can be created by
using Fast Snap.
Cloning pairs includes operations after the P-VOL is copied to the S-VOL, until volumes are unpaired.
Volumes created by cloning are not included.
Snapshot trees and cascaded pairs
The volume in the top layer of the snapshot tree is the root volume. Volumes in the bottom layer are leaf
volumes.
14 Snapshot Clones
Creating cascaded pairs
Fast Snap S-VOLs can be paired with secondary layer S-VOLs. First layer (L1) S-VOLs can also be
paired with secondary layer (L2) S-VOLs. A maximum of 64 layers can be created, and a maximum of
1,024 S-VOLs can be used for a P-VOL. In this case, the snapshot tree is cascaded.
L2 to L64 pairs are called cascaded pairs. The following figure illustrates the configuration of cascaded
snapshot trees.
Creating cascaded pairs 15
• The volume in the top layer of the snapshot tree (P-VOL of the L1 pair) is the root volume.
• Volumes between the root and leaf volumes are node volumes.
• Volumes in the bottom layer of the snapshot tree are leaf volumes.
To create a Fast Snap pair that can be used in a cascaded snapshot tree, open the Create FS Pairs
window and select Enable for Cascade in RWC or use the raidcom add snapshot -snap_mode
cascade command in RAID Manager. For details, see Creating Fast Snap pairs using Remote Web
Console on page 114 or Adding Fast Snap pairs to snapshot or consistency groups using RAID
Manager on page 119.
When the S-VOL of a Fast Snap pair you created for a P-VOL for the first time is a THP V-VOL, you can
create cascaded pairs. If a Fast Snap pair whose secondary volume is a Fast Snap V-VOL (which has the
Snapshot provisioning type) is created, remove the pair first, and then create another Fast Snap pair
whose secondary volume is a THP V-VOL.
16 Overview of Fast Snap
A snapshot tree can be configured by combining snapshot and cloned pairs. As shown in the following
figure, you can also cascade pairs that are being cloned, but you can only clone up to three pairs
concurrently. The following figure shows an example of when pairs that are being cloned are also
cascaded.
You can use the S-VOL of a cascaded and cloned pair as a new L1 pair of the P-VOL. In this case, the
volume is the root volume, and a node or leaf volume.
Volume differences between Fast Snap and Business Copy
The following table summarizes the volume and other differences between Fast Snap and Business
Copy.
Volume differences between Fast Snap and Business Copy 17
Item Fast Snap Business Copy
Initial copy operation
Number of S-VOLs per P-VOL Up to 1,024 Up to 9
Capacity efficiency High. Only differential data is
Operation of copied volumes Always used with the P-VOL. Can be used separately from the
P-VOL physical failures S-VOL data cannot be
S-VOL or pool physical failures If a physical failure occurs in a
*When a pool is full (the depletion threshold is exceeded in a pool for which the capacity for Fast Snap
pairs is limited), data in all S-VOLs using the pool cannot be guaranteed.
The following figures explain the relation of data when a failure occurs in the P-VOL.
Not required.
Volumes can be copied faster.
copied from the P-VOL.
guaranteed.
pool*, data in all S-VOLs that use
the pool cannot be guaranteed.
Required.
Low. The entire P-VOL is copied.
P-VOL.
P-VOL data can be restored
using the S-VOL.
If a physical failure occurs in an
S-VOL, data in the S-VOL cannot
be guaranteed.
Fast Snap S-VOLs reference data in the P-VOL. Therefore, if a failure occurs in the P-VOL, data in all SVOLs under the P-VOL is lost.
18 Overview of Fast Snap
Business Copy S-VOLs retain all P-VOL data. Therefore, if a failure occurs in the P-VOL, data in the SVOLs is not lost.
The following figure explains the relation of data when a failure occurs in a pool.
Fast Snap S-VOLs reference data in the pool. If the pool cannot be used because a failure occurs in the
pool or the pool becomes full, data in all S-VOLs that use the pool is lost. In addition, if a pool failure
occurs or the pool becomes full during restoration, data in the P-VOL which is being restored cannot be
used.
The following figure explains the relation of data when a failure occurs in an S-VOL.
Overview of Fast Snap 19
For Business Copy, each S-VOL independently retains data. Therefore, only data in the failed S-VOL is
affected. In addition, if a failure occurs in an S-VOL during restoration, data in the P-VOL which is being
restored cannot be used.
XP7 Storage software applications for Fast Snap
Fast Snap
Use the Fast Snap software on the Remote Web Console (RWC) computer that is connected to the
service processor (SVP) by means of the TCP/IP local area network (LAN).
Thin Provisioning
Use the THP software on the RWC computer. A user license is required to use THP.
Since Fast Snap uses a portion of the THP licensed capacity for its pool capacity, reserve enough THP
licensed capacity to run both THP and Fast Snap and to accommodate the Fast Snap pairs or pools that
you will create.
Fast Snap and THP pool-VOLs are also referred to as used volumes. The licensed capacity must exceed
the total capacity of used volumes.
RAID Manager
When you use RAID Manager to define multiple Fast Snap pairs in a consistency group, you can only
specify one consistency group for a group defined by the configuration definition file for RAID Manager.
NOTE: The configuration definition file for RAID Manager is a group that is not a consistency group.
If you create a new pair and define the pairs in a consistency group for a group you defined using the
configuration definition file for RAID Manager, and the pair is already defined in a consistency group, the
pair is defined in the same consistency group even if you try to create a new pair and assign it to a
different consistency group.
More information
Splitting Fast Snap pairs to store snapshot data using RAID Manager on page 121
20 XP7 Storage software applications for Fast Snap
How Fast Snap works
How Fast Snap uses pools and pool volumes
Fast Snap stores snapshot data in THP pools (Pool Type: Thin Provisioning) or Fast Snap pools (Pool
Type: Fast Snap). Unless they are defined otherwise, both THP pools and Fast Snap pools are referred to
as "pools". A pool consists of multiple pool volumes (pool-VOLs) which are, as a group, the container for
the snapshot data.
You must create pools to use Fast Snap. You can create pools and add and delete pool-VOLs from them
using Fast Snap.
The following figure illustrates the relationship between a Fast Snap pair and a pool.
CAUTION: When creating pools, calculate the pool capacity and reserve a sufficient amount of pool
capacity. When you write data to Fast Snap pair volumes and the amount of pool usage exceeds
the pool capacity, the Fast Snap pair is suspended (“PSUE” status), snapshot data is not stored,
and you cannot create additional Fast Snap pairs.
More information
Creating Fast Snap data pools on page 89
Increasing pool capacity on page 155
Decreasing pool capacity on page 159
Deleting pools on page 170
Restoring suspended Fast Snap pairs on page 126
Usage level rebalancing among parity groups
Rebalancing is performed as if each parity group were a single pool-VOL. After rebalancing, the usage
rates of LDEVs in a parity group may not be balanced, but the usage rate in the entire pool is balanced.
How Fast Snap works 21
The usage level among parity groups is automatically rebalanced when expanding or shrinking pool
capacity operations are in progress.
If you expand the pool capacity, Thin Provisioning moves data to the added space on a per-page basis.
When the data is moved, the usage rate among parity groups of the pool-VOLs is rebalanced.
Host I/O performance may decrease when data is moved. If you do not want to have the usage level of
parity groups automatically balanced, call HPE technical support.
You can see the rebalancing progress of the usage level among parity groups in the View Pool
Management Status window in RWC. In RAID Manager, you can use the raidcom get pool -key
command to see if the usage levels among parity groups are rebalanced. Thin Provisioning automatically
stops balancing the usage levels among parity groups if the cache memory is not redundant or the pool
usage rate reaches up to the threshold.
More information
Viewing formatted pool capacity and pool usage rates on page 154
How Fast Snap uses V-VOLs
Fast Snap uses Fast Snap V-VOLs (V-VOLs of provisioning type Snapshot in RWC, or V-VOLs created by
the raidcom add ldev -pool snap command in RAID Manager) or THP V-VOL as V-VOLs. Fast
Snap V-VOLs and THP V-VOLs are referred to as virtual volumes (V-VOLs) in this document. Use THP VVOLs to create cascaded or cloned pairs. Use Fast Snap V-VOLs to create snapshot pairs. Note that you
can use THP V-VOLs to cascade snapshot pairs.
Fast Snap uses V-VOLs to access snapshot data from hosts or clone pairs, so if you create clone pairs or
use snapshot pairs (a pair with the snapshot attribute) to access snapshot data from hosts, then V-VOLs
are required to create Fast Snap pairs or assign an S-VOL to snapshot data. If the storage system or
snapshot pair does not need to access snapshot data from hosts, V-VOLs are not necessary.
You can release the V-VOLs that are being used as Fast Snap S-VOLs from assignment of snapshot
data. Released V-VOLs can be assigned to other snapshot data. However, you cannot release allocation
of V-VOLs used as node volumes to snapshot data or allocate the V-VOL to different snapshot data. Also,
you cannot release allocation of V-VOLs which are being used for the S-VOL of a clone pair to snapshot
data, or allocate it to different snapshot data.
If you release a V-VOL being used as a Fast Snap S-VOL from assignment to snapshot data, and then
assign the V-VOL to different snapshot data, this V-VOL becomes the S-VOL of another pair. Therefore,
each time you assign a V-VOL to snapshot data, execute the command which allows the host server to
recognize the device.
You cannot release definitions of V-VOLs if the V-VOLs are being used as Fast Snap secondary volumes;
you must first release the Fast Snap pairs that are using the V-VOLs.
How Fast Snap pairs are created
Create Fast Snap pairs in the Create FS Pairs window in RWC, or by using the raidcom add
snapshot command in RAID Manager.
When creating a Fast Snap pair, you need to specify the pool to be used for the pair. If multiple Fast Snap
pairs share the same primary volume, the pairs must also share the same pool. For example, if you
specify three secondary volumes for one primary volume, you must specify the same pool for the three
Fast Snap pairs.
If you release a Fast Snap pair, the volume status becomes SMPL. Immediately after a volume becomes
SMPL, you cannot use the volume to create a Fast Snap pair. If you want to create Fast Snap pairs using
SMPL volumes, you should wait for a while before creating the pairs. The wait time required depends on
your system environment.
22 How Fast Snap uses V-VOLs
You can check the status of volumes in the Local Replication window and the View Pair Properties
window in RWC, or by using the raidcom get snapshot command in RAID Manager.
More information
Creating Fast Snap pairs using Remote Web Console on page 114
Viewing pair properties on page 140
Using snapshot pairs (not cascaded)
Data in the P-VOL is backed up one time every day. The P-VOL can be restored using the S-VOL if a
logical failure occurs during data update or if there is a virus in the P-VOL.
Using cascaded pairs
Distributing data in the P-VOL to multiple users
Create the same number of leaf volumes as the number of users to whom you want to distribute data.
This allows you to distribute data in the P-VOL without increasing loads to the P-VOL.
Using snapshot pairs (not cascaded) 23
24 Overview of Fast Snap
Distributing updated data in the P-VOL to specified users
When you update the P-VOL and want to give it only to the specified users (S-VOLs 5 and 6 in the
figure), do the following:
1. Create cascaded pairs, and distribute data in the P-VOL. Assign users to whom you want to distribute
the updated data, and users to whom you do not want to distribute the updated data to separate node
volumes.
2. Delete the pairs in the node volume where you assigned users you do not want to distribute the
updated data to (S-VOL 1 in the figure).
3. Update the P-VOL.
Overview of Fast Snap 25
Creating a new distributor with cloned pairs
1. Create cascaded pairs and distribute data in the P-VOL. Assign the clone attribute to the volume to be
a new distributor (S-VOL 3 in the figure).
2. Clone pairs.
By cloning pairs, S-VOL 3 and S-VOL 1 become unpaired volumes (THP V-VOLs) in the same status,
and S-VOL 3 can be a new distributor. As a result, the overhead of the Fast Snap pairs can be reduced.
Workflow for creating groups and storing snapshot data using RAID Manager
With Fast Snap, Business Copy, and Business Copy MF, you can create up to 2,048 consistency groups
in an XP7 Storage system.
The following figure illustrates how snapshot data is stored for a consistency or snapshot group using
RAID Manager raidcom commands.
26 Workflow for creating groups and storing snapshot data using RAID Manager
Use the following workflow to create a snapshot group and store volume snapshot data in the group:
1. Split the pair and store snapshot data for a group. To do this using RAID Manager, run the following
raidcom command:
raidcom modify snapshot -snapshot_data create
2. The host issues a write request to each P-VOL in the group.
Snapshot data for the volumes are stored.
A RAID Manager command is used to store snapshot data for a consistency group or a snapshot group.
Remote Web Console can only be used to reference consistency groups and snapshot groups.
More information
Consistency and snapshot groups on page 13
Creating Fast Snap pairs using Remote Web Console on page 114
Overview of Fast Snap 27
Removing Fast Snap snapshot groups on page 130
Pair tasks using RAID Manager or Remote Web Console on page 194
Methods of storing snapshot data
In the CAW method, writing the P-VOL snapshot data changes the status to “write completion”. In the
COW method, storing the P-VOL snapshot data changes the status to "write completion". The CAW
method wait time is shorter than that of the COW method.
Workflow for the CAW method
The following workflow describes the CAW method and how an XP7 Storage system stores snapshot
data:
1. The host writes data to a P-VOL.
2. The storage system returns the write completion status to the host.
3. The storage system stores snapshot data for the P-VOL in the background.
The following figure illustrates the CAW method.
Workflow for the COW method
The following workflow describes the COW method and how an XP7 Storage system stores snapshot
data:
1. The host writes data to a P-VOL.
2. The storage system stores snapshot data for the P-VOL.
3. The storage system returns the write completion status to the host.
The following figure illustrates the COW method.
28 Methods of storing snapshot data
Fast Snap pair restoration
Overwriting snapshot data to P-VOLs is also referred to as restoring Fast Snap pairs.
If data is written to a secondary volume, this particular data (not snapshot data) is overwritten to the
primary volume when the Fast Snap pair is restored.
If a problem occurs in P-VOL data due to a failure, restoring the pair restores the P-VOL data saved when
the snapshot data was stored. However, if the pair status is PSUE, the pair cannot be restored.
The time for restoring a Fast Snap pair depends on the following, even if the pair synchronization rate is
100%:
• The amount of pool capacity a pair is using.
• The number of pairs being operated concurrently.
The pair synchronization rate shows the rate that S-VOL data matches that of the next generation of the
S-VOL. If the S-VOL is the latest one, the synchronization rate is computed by comparing the S-VOL with
the P-VOL.
For the Fast Snap pair where the cascade attribute is enabled, the information displayed in
Synchronization Rate (%) of the View Pair Synchronization Rate window varies depending on the pair
status.
More information
Restoring Fast Snap pairs on page 124
How Fast Snap pair status changes
The following figure illustrates status changes to Fast Snap and snapshot pairs.
Fast Snap pair restoration 29
The following workflow describes the Fast Snap pair status changes:
1. You choose two volumes that are in SMPL status and are not in use as a Fast Snap pair.
2. You create a pair. If the primary volume has not previously been paired with any secondary volume,
the pair status changes to "COPY" at first, and then to "PAIR" after the pair creation finishes.
• Creation of a Fast Snap pair may be time consuming if you create a pair immediately after deleting
the last snapshot data for the primary volume.
• If the pool threshold is exceeded when the Fast Snap pair is in "PAIR" status, the pair status
changes to "PFUL."
• Fast Snap pairs cannot be created when the pool threshold (warning threshold when snapshot data
is stored in a THP pool) is exceeded.
3. Snapshot data is stored when you split a pair in "PAIR" status. After snapshot data is stored, the pair
status is "PSUS." If the pool threshold is exceeded when the Fast Snap pair is in "PSUS" status, the
pair status changes to "PFUS."
4. If you only want to delete snapshot data but do not want to release the Fast Snap pair, you delete the
snapshot data for the pair in "PSUS" or "PFUS" status.
30 Overview of Fast Snap
Loading...