HP XP12000, SVS200, XP10000 User Manual
HP StorageWorks
Business Copy XP user guide
for the XP12000/XP10000/SVS200
Part number: T1713-96007
ifth edition: March 2007
F
Legal and notice information
© Copyright 1999, 2007 Hewlett-Packard Development Company, L.P.
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Microsoft, Windows, Windows XP, and Windows NT are U.S. registered trademarks of Microsoft Corporation.
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Contents
Aboutthisguide .......................... 7
Intendedaudience...................................... 7
Prerequisites ........................................ 7
Relateddocumentation.................................... 7
Documentconventionsandsymbols .............................. 8
HPtechnicalsupport..................................... 8
Subscriptionservice ..................................... 9
HPwebsites......................................... 9
Documentationfeedback ................................... 9
1BusinessCopyXP(BC)fortheArray ................. 11
OverviewofBCoperations .................................. 11
BCcomponents..................................... 11
BCvolumepairs(P-VOLsandS-VOLs)......................... 12
CopyThresholdoption............................... 13
Cascadepairs .................................. 13
BCsoftwareontheCommandViewXPmanagementstation............... 13
BCrequirementsforthearray .............................. 13
Maximumnumberofpairsforthearray........................ 15
BCoperations..................................... 21
Setreserveattributeoperation............................ 21
Resetreserveattributeoperation........................... 21
Paircreateoperation ................................ 21
Initialcopyoperation................................ 21
Updatecopyoperation............................... 22
Cascadefunction ................................. 23
Pairsplitoperation................................. 23
Pairresyncoperations................................ 24
Forwardpairresyncoperation ............................ 25
Backwardpairresyncoperation ........................... 25
Pairstatusandtimerequiredforpairresync ...................... 30
Pairsplit-Eoperation(suspend)............................ 30
Pairsplit-Soperation(delete)............................. 31
BCoptions...................................... 31
Swap&Freezeoption................................ 31
HostI/OPerformanceoption ............................ 32
Cascadefunction ................................... 32
At-TimeSplitfunction.................................. 36
EnablingtheAt-TimeSplitfunctionusingRAIDManager................. 37
Pairstatus ...................................... 38
Cautionsonswitchingoffthepowersupply ........................ 40
CautionsonusingtheXP10000............................. 41
PreparingforBCoperations................................. 41
Systemrequirements .................................. 41
PreparingforBCoperations............................... 42
CombiningBCwithotherdatamanagementoperations................... 43
CombiningBCandContinuousAccessXPJournaloperations................. 43
CombiningBCandContinuousAccessXPoperations.................... 46
CombiningBCwithLUNSecurityXPExtension....................... 49
Copyingaccessattributes................................ 49
License capacity of LUN Security XP Extension . . . . . . . . . . . . . . . . . . . . . . . 51
Business Copy XP user guide
3
StartingBC........................................ 52
BCmainscreen.................................... 53
Volumelist .................................... 55
Detailwindow................................... 57
S-VolPathwindow................................. 58
DisplayFilterwindow ............................... 59
PresetVolumelist ................................. 60
PerformingBCoperations.................................. 61
Settingreserveattributes ................................ 61
ReservingoneormorevolumesforuseasBCS-VOLs.................. 61
Resettingreserveattributes ............................... 62
Unreservingoneormorevolumes .......................... 62
CreatingBCpairs(Paircreate).............................. 63
PaircreateVolumeList................................ 64
CopyPacelist................................... 64
SelectMUlist................................... 64
SelectS-Volbox.................................. 65
Buttons...................................... 65
CreatingL1pairs ................................. 66
CreatingL2pairs ................................. 67
SplittingBCpairs(Pairsplit) ............................... 67
PairsplitVolumeList ................................ 67
Windowoptions.................................. 68
SelectS-Volbox.................................. 68
Buttons...................................... 69
Splittingpairs................................... 69
Creatingandsplittingpairs............................. 70
ResynchronizingBCpairs(Pairresync)........................... 71
PairresyncVolumeList ............................... 71
Windowoptions.................................. 72
ResynchronizingoneormoreBCpairs ........................ 72
SuspendingBCpairs(Pairsplit-E)............................. 73
SuspendingoneormoreBCpairs .......................... 73
DeletingBCpairs(Pairsplit-S) .............................. 74
DeletingoneormoreBCpairs............................ 74
ViewingBCpairstatusandhistory............................ 74
SettingBCoptions................................... 76
SettingaBCoption(Swap&Freezeoption)....................... 77
BCerrorcodes .................................... 77
Index .............................. 83
4
Figures
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26 ..BCmainscreen ................................ 53
27
28
29
30
31
32
33
34
35
36
37
38
39
40
..BCoverview.................................. 12
..AddingapairinBC .............................. 22
..Update copy o
..Normalandquickpairresyncoperations...................... 25
..Reverseandquickrestorepairoperations ..................... 27
..BC P-VOL forming pair with Continuous Access XP S-VOL and external S-VOL, respectively . 29
..BC P-VOL forming pair with external S-VOL and shared as Continuous Access XP S-VOL . . 29
..BC S-VOL forming pair with external P-VOL and shared as Continuous Access XP P-VOL . . 29
..BCP-VOLformingpairwithCAXPJou.S-VOLandExt.S-VOL,respectively....... 29
..BC P-VOL forming pair with external S-VOL and shared as Continuous Access XP Journal S-VOL 29
..Quick Rest
..Cascadepairs................................. 33
..OverviewofAt-TimeSplitfunction......................... 37
..BCpairstatustransitions ............................ 38
..BCandContinuousAccessXPJournal:SharedP-VOLandP-VOL ........... 44
..BCandContinuousAccessXPJournal:SharedP-VOLandS-VOL ........... 45
..BC and Continuous Access XP Journal: Shared P-VOL and P-VOL and P-VOL and S-VOL . . 45
..BCandContinuousAccessXP:sharedP-VOL/P-VOL................. 46
..BC and C
..BCandContinuousAccessXP:sharedP-VOL/P-VOLandP-VOL/S-VOL......... 47
..BCandContinuousAccessXP:sharedS-VOL/P-VOL................. 48
..BC, Continuous Access XP Journal, and Continuous Access XP: Shared S-VOL/P-VOL/S-VOL 48
..BC, Continuous Access XP, and Continuous Access XP Journal: Shared S-VOL/P-VOL/S-VOL 49
..Copyingaccessattribute ............................ 50
..Required license capacity for LUN Security XP Extension when using cascade function . . 52
..Volumelist................................... 56
..Detailwindow................................. 58
..S-VolPathwindow ............................... 58
..DisplayFilterwindow(BCtabselected) ...................... 59
setVolumelist................................ 60
..Pre
..
SetReserveAttributewindow........................... 61
..ResetReserveAttributewindow.......................... 62
..Paircreatewindow ............................... 63
..Pairsplitwindow ................................ 67
..Pairresyncwindow ............................... 71
..Pairsplit-Ewindow ............................... 73
..Pairsplit-Swindow ............................... 74
istorypane.................................. 75
..H
..Optionscreen ................................. 76
peration ............................. 23
ore operation with or without Swap&Freeze option . . . . . . . . . . . . . 32
ontinuousAccessXP:sharedP-VOL/S-VOL................. 47
Business Copy XP user guide
5
Tables
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19 ..BC tree
20
21
22
23
..Documentconventions............................... 8
..BCoperationalrequirementsforthearray ..................... 14
..Totalnumberofdifferentialtablesperpair..................... 17
..Numberofcontrolcylindersaccordingtoemulationtypes .............. 17
..Relationship between emulation type, capacity, and differential tables . . . . . . . . . 18
..NumberofdifferentialtablesusedinOPEN-V ................... 18
..Requirements for reverse or quick restore pairresync operations . . . . . . . . . . . . 28
..BCoptionstypesandrequirements ........................ 31
..RelationshipbetweenL1pairstatusandL2pairoperations.............. 34
..RelationshipbetweenL2pairstatusandL1pairoperations.............. 35
..Read/wri
..Read/write operation (host to the leaf volume) and L2 pair status . . . . . . . . . . . 36
..BCpairstatusconditions ............................ 40
..IdentifyingthevolumesforBCoperations ..................... 42
..AccessattributeandavailabilityasaBCpairvolume ................ 49
..Availability of BC operations on volumes with the S-VOL Disable attribute . . . . . . . . 49
..VMAsettingandavailabilityofPaircreateoperation................. 50
..PairstatusandavailabilityofLUNSecurityXPExtensionoperations .......... 51
..StatusiconsforBC............................... 54
..BCoperationsshortcutmenucommands...................... 57
..BCpairactivitycodes,messages,anddescriptions ................. 76
..BCerrorcodes................................. 77
te operation (host to the node volume) and L1/L2 pair status . . . . . . . . . 35
icons ................................. 53
6
About this guide
This guide provides information about:
• using Business Copy XP operations
• preparing Business Copy XP operations
• starting Business Copy XP operations
• performing Business Copy XP operations
• understanding Business Copy XP operation error codes
Intended audience
This guide is
• Disk array hardware and software
• Data processing and RAID storage subsystems and their basic functionsand utilities
Prerequisites
Prerequisites for using this product include:
• Installation of the HP StorageWorks disk array(s)
• Installation of the license key for this product
intended for customers and HP-authorized service providers with knowledge of:
Related do
The following documents provide related information:
• HP StorageWorks Command View XP user guide for XP Disk Arrays
• HP Storage
• HP StorageWorks Snapshot XP user guide
• HP StorageWorks LUN Configuration and Security Manager XP user guide for the
XP12000/XP10000
• HP Storag
• HP StorageWorks RAID Manager XP user guide
• Hitachi ShadowImage for z/OS user guide
• HP Stora
• HP StorageWorks Performance Control XP user guide
• HP StorageWorks Flex Copy XP user guide
You can find these documents from the Manuals page of the HP Business Support Center website:
ttp://www.hp.com/support/manuals
h
In the S
cumentation
Works XP Remote Web Console user guide for XP12000/XP10000
eWorks LUN Security XP Extension user guide
geWorks External Storage XP user guide
torage section, click Storage Software and then select your product.
Business Copy XP user guide
7
Document conven
Table 1 Document conventions
tions and symbols
Convention
Blue text: Table 1
Blue, underlined text: http://www.hp.com
Bold text
Italic text Text emphasis
Monospace text
Monospace, italic text
Monospace, bold text
Element
Cross-reference links and e-mail addresses
website addresses
• Keys that are p
• Text typed in
• GUI elements
menu and lis
• File and directory names
• System output
• Code
• Commands, their arguments, and argument values
• Code variables
• Command variables
Emphasized monospace text
ressed
to a GUI element, such as a box
that are clicked or selected, such as
t items, buttons, tabs, and check boxes
CAUTION:
Indicates that failure to follow directions could result in damage to equipment or data.
IMPORTANT:
Provides clarifying information or specific instructions.
NOTE:
Provides additional information.
TIP:
Provides helpful hints and shortcuts.
HP technical support
For worldwide technical support information, see the HP support website:
ttp://www.hp.com/support
h
Before contacting HP, collect the following information:
• Product model names and numbers
• Technical support registration number (if applicable)
• Product serial numbers
• Error messages
• Operating system type and revision level
8
About this guide
• Detailed questions
Subscription s
HP recommends t
h
ttp://www.hp
After register
firmware updat
ervice
hatyouregisteryourproductattheSubscriber'sChoiceforBusinesswebsite:
.com/go/e-updates
ing, you will receive e-mail notification of product enhancements, new driver versions,
es, and other product resources.
HP websites
For additional information, see the following HP websites:
•h
ttp://www.hp.com
•http://www.hp.com/go/storage
•http://www.hp.com/service_locator
•http://www.hp.com/support/manuals
Documentation feedback
HP welcomes your feedback.
To make comm
storagedoc
ents and suggestions about product documentation, please send a message to
s.feedback@hp.com. All submissions become the property of HP.
Business Copy XP user guide
9
10
About this guide
1 Business Copy XP (BC) for the
Array
HPStorageWorksBusinessCopyXP(BC)maintainsinternalcopiesofuserdataondiskarraysfor
purposes such as data backup or duplication. Duplicate volumes are created on the same disk array as
the primary volume at hardware speeds. BC is used for UNIX and PC server data, and can provide up to
nine duplicates of one primary volume.
This chapter provides instructions for performing BC operations using Command View XP or XP Remote
Web Console.
NOTE:
See the
for instructions on accessing Business Copy from Command View XP Advanced Edition.
BC operations are nondisruptive and allow the primary (main) volume of each volume pair to remain
online to all hosts for read and write I/O operations.
After establishing operations, BC operations continue unattended to provide asynchronous internal
data backup. Usability is further enhanced through a resynchronization capability that reduces data
duplication requirements and backup time, thereby increasing user productivity. BC also supports reverse
resynchronization.
HP StorageWorks Command View XP Advanced Edition Device Manager Web Client user guide
You can perform BC operations in conjunction with HP StorageWorks Continuous Access XP operations
to provide additional remote copies of BC volumes. BC also supports the disk array's custom volume
size (CVS) and Cache LUN features, ensuring that BC operations can duplicate all user data. See
Combining BC with other data management operations for further information on combining BC with
other data management features.
You can also perform BC operations with External Storage XP operations to create pairs with external
volumes.
Overview of BC operations
BC is a storage-based hardware solution for duplicating logical volumes that reduces backup time
and provides point-in-time backup. BC primary volumes (P-VOLs) contain original data; BC secondary
volumes (S-VOLs) contain duplicate data. You can use the BC cascaded volume function to make up to
nine copies of each P-VOL. Because each S-VOL is paired with its P-VOL independently, each S-VOL can
be maintained as an independent copy set that can be split, resynchronized, and deleted separately
from other S-VOLs assigned to the same P-VOL.
BC components
BC operations on the Command View XP management station or XP Remote Web Console involve
primary and secondary volumes in the disk array. Figure 1 shows a typical BC configuration. BC
system components are:
• BC volume pairs (P-VOLs and S-VOLs)
• BC software on the Command View XP management station
Business Copy XP user guide
11
Figure 1 BC overview
Use BC from the Command View XP management station or XP Remote Web Console to make local
copies of volumes. The volume that has original data is called a P-VOL (primary volume), and a volume
to which data is copied is called an S-VOL (secondary volume). Pairs of P-VOLs and S-VOLs made by BC
are called BC pairs. You can specify an S-VOL as a P-VOL to make another two BC pairs. As a result,
you can use BC to make a total of nine S-VOLs. Use the cascade style to make BC pairs by specifying
S-VOLs as P-VOLs. In cascade style, pairs in the first cascade layer are called L1 pairs and pairs in
the second cascade layer are called L2 pairs.
BC volume pairs (P-VOLs and S-VOLs)
Disk arrays contain and manage original and copied BC data. The XP1024/XP128 disk arrays support a
maximum of 8,190 BC volumes: 4,095 pairs and the RAID Manager command device. The XP12000
disk array supports a maximum of 16,382 BC volumes (8,191 pairs: (8,191 P-VOLs and 8,191 S-VOLs) and
the RAID Manager command device. When BC pairs include size-expanded LUs, the maximum number
of pairs decreases. When pairs include more than one S-VOL, the maximum number of P-VOLs decreases.
BC performs copy operations for logical volume pairs that you establish. Each BC pair consists of one
primary volume (P-VOL) and up to three secondary volumes (S-VOLs). These volumes can be located
in the XP disk array or in external storage attached to the XP disk array. BC S-VOLs are secondary or
mirrored volumes containing backup data. Each S-VOL must be paired with only one P-VOL. During BC
operations, P-VOLs remain available to all hosts for read and write I/O operations (except during reverse
resync and quick restore). S-VOLs become available for host access only after the pair is split.
When a BC volume pair is created, data on the P-VOL is copied to the S-VOL to synchronize the volumes.
During this initial copy operation and after the pair is synchronized, all write operations to the S-VOL are
prohibited. To access an S-VOL, you can “split” the pair to make the S-VOL accessible. While a BC pair
is split, the disk array keeps track of all changes to the P-VOL and S-VOL. When you “resync” the pair, the
12
Business Copy XP (BC) for the Array
differential data in the P-VOL (due to P-VOL and S-VOL updates) is copied to the S-VOL, so the S-VOL is
again identical to the P-VOL. For reverse resync, the differential data in the S-VOL (due to P-VOL and
S-VOL updates) is copied to the P-VOL, so the P-VOL is now identical to the S-VOL.
NOTE:
BC S-VOLs are updated asynchronously. For a volume pair with PAIR status, the P-VOL and S-VOL may
not be identical. For further information on BC update copy operations, see Paircreate operation.
BC P-VOLs or S-VOLs should not be concentrated in the same RAID group. To disperse workloads of
RAID groups, each RAID group should have both P-VOLs and S-VOLs evenly distributed. BC pairs for
which BC operations are performed simultaneously should be in different RAID groups. If BC pairs are
concentrated in only a few RAID groups, host I/O performance may be degraded.
If the disk array is overloaded, increase cache, disk adapters, and/or RAID groups. Consider assigning
BC S-VOLs in newly installed RAID groups. If you continue BC operations with an overloaded disk
array, host I/O performance may be degraded.
Copy Threshold option
If BC performs copy operations when the disk array workload is heavy, host server I/O performance
might be degraded. To minimize this performance degradation, enable Copy Threshold,which
temporarily stops all BC copy operations when the disk array has a heavy workload. Copy operations
that are stopped by the Copy Threshold option resume when the disk array workload is lighter.
This option is different from the Host I/O Performance option (Host I/O Performance option), because it is
effective only when the disk array workload is heavy.
NOTE:
Contact your HP support account representative for more information about the Copy Threshold option.
In addition to BC operations, Copy Threshold temporarily stops copy operations for the following
applications when the disk array workload is heavy:
• Auto LUN XP
• ShadowImage for z/OS
• Hitachi FlashCopy Mirroring
• Hitachi FlashCopy Mirroring Version 2
• Snapshot XP
• Flex Copy XP
Cascade pairs
The BC cascade function adds a second layer of pairs onto the first layer of original BC pairs. Use these
two layers of pairs (L1 and L2) to create and maintain up to nine copies of one original BC primary
volume (P-VOL). See Cascade function for further information on the cascade function.
BC software on the Command View XP management station
When installed on the Command View XP management station, the BC software displays BC information
and performs BC operations. The Command View XP management station can be attached to multiple
disk arrays. The Command View XP management station acquires status from and issues commands to
BC P-VOLs and S-VOLs.
BC re
quirements for the array
BC operations provide local copies of UNIX/PC server volumes (LUs) on the disk array. The following
table describes the operational requirements for BC.
Business Copy XP user guide
13
Table 2 BC operational requirements for the array
Parameter
Pair objects Logical device
Number of copies Maximum of three copies (S-VOLs) per primary volume (P-VOL). Maximum of one
Requirement
s (LDEVs): OPEN-x (such as OPEN-3, OPEN-9, OPEN-E, and
OPEN-V), inclu
configured. The P-VOL and S-VOL must be the same type (for example, OPEN-3
to OPEN-3 is allowed, OPEN-3 to OPEN-9 is not allowed).
AcustomsizeP-VOLmustbepairedwithS-VOLsofthesametypeandcapacity.
ALUSEP-VOLmustbepairedwithS-VOLsofthesamesizeandstructure.For
example, if a LUSE P-VOL is connected to volumes of 1GB, 2GB, and 3GB in
this order, you must specify the LUSE volume that has exactly the same size and
connection order as the S-VOL.
BC does not support multiplatform devices (for example, 3390-3A, -3B, -3C).
For information about using Snapshot XP pair volumes as Business Copy XP
volumes, pl
Snapshot XP
P-VOLs or SJournal vo
specified as P-VOLs or S-VOLs.
Volumes that form a Flex Copy XP pair cannot be specified as P-VOLs. A Flex
Copy XP P-VOL can be specified as a Business Copy XP S-VOL under certain
conditions. Refer to the HP StorageWorks Flex Copy XP user guide for more
informat
BC operat
pairs th
same conditions applied to the volumes in the local disk array. Refer to the HP
StorageWorks External Storage XP user guide for more information.
P-VOL per S-VOL (P-VOLs cannot share an S-VOL).
An additional six copies can be created by using the BC cascade function.
ding CVS and LUSE volumes. Devices must be installed and
ease refer to Snapshot XP User’s Guide.
pairs, virtual volumes, and pool volumes cannot be specified as
VOLs.
lumes for HP StorageWorks Continuous Access XP Journal cannot be
ion.
ions can be performed with External Storage XP operations to create
atusetheexternalvolumesasBCS-VOLs(ormirroringvolumes)underthe
Maximum number of
1
pairs
mum number of
Maxi
Ls
S-VO
MU (mirror unit) numbers
of cascade pairs
Combinations of
RAID levels (primarysecondary)
Dynamic sparing and
automatic correction
copy
A maximum of 8,192 pairs (8,192 P-VOLs and 8,192 S-VOLs) can be created
per disk array.
NOTE:
The maximum number of pairs equals the total number of BC, Snapshot XP,
ShadowImage for z/OS, Hitachi FlashCopy Mirroring, Hitachi FlashCopy
Mirroring Version 2, Auto LUN XP, and Flex Copy XP volume pairs.
When you use RAID Manager, the command device reduces the maximum
n u mber o f B C p a i r s t o 8 ,191 ( 8 ,191 P - VO Ls a n d 8 ,191 S - VO L s ) w hen c o n figuring
pairsinaratioof1S-VOLto1P-VOL.
IfsomeBCpairscontainLUSEvolumes,orifanapplicationotherthanBCisused,
the maximum number of BC pairs might be less than 8,192 (or 8,191).
Refer to Maximum number of pairs for the array Maximum number of pairs for
the array” on page 15 for information about calculating the maximum number
of BC pairs.
2(8,191ifRAIDManagerisused).
8,19
L1 pairs = 0, 1, and 2 (a total of 3 pairs)
L2pairs=1and2(atotalof2pairs)
All combinations supported: RAID1-RAID1, RAID5-RAID5, RAID6-RAID6,
RAID1-RAID5, RAID1-RAID6, RAID5-RAID1, RAID5-RAID6, RAID6-RAID1,
RAID6-RAID5.
failure occurs requiring the disk array to utilize dynamic sparing or automatic
If a
correction copy, the status of the paired volumes associated with the failed
physical device is not affected.
14
Business Copy XP (BC) for the Array
Parameter
Requirement
Physical device (PDEV)
maintenance
Logical device
maintenance
Cache maintenance
Point-in-time backup
s
Failure
Maintenance/upgrade
(LDEV)
Maintenance of a PDEV that is not used by BC does not affect BC operations or
the status of BC pairs. If a PDEV contains LDEVs used by BC, you can maintain
that PDEV independently of the BC operations and pair status.
If the status of a BC pair is COPY(PD), PAIR, PSUS, PSUS(SP), COPY(SP),
COPY(RS), or COPY(RS-R), maintenance for the LDEVs used by that pair is
restricted. Maintenance is also restricted for LDEVs with the Reserve attribute.
To maintain these LDEVs, suspend or delete the BC pair, or reset (unreserve)
the Reserve attribute.
If disk array cache maintenance is performed during a period of high I/O usage,
one or more BC pairs may be suspended. Reduce the I/O load before cache
maintenance.
For pairs in PAIR status, host I/Os are copied to S-VOLs asynchronously. To
synchronize a pair and access the S-VOL as soon as possible, take the P-VOL
offline and split the pair before using the S-VOL. If the P-VOL cannot be taken
offline, a P.I.T. backup still occurs if a pairsplit is issued. When all data on the
P-VOL (up to the pairsplit time) is copied to the S-VOL, the pair is split and the
S-VOL becomes available for use (R/W). The operation may take longer to
complete if high write activity from the host to the P-VOL is occurring. A P.I.T.
backup can also be performed by issuing a pairsplit to P-VOLs in the SMPL
(simplex) state (in this case the pairsplit operation simultaneously creates and
splits new BC pairs.).
When a failure of any kind prevents a BC copy operation from completing, the
ay suspends the pair. If an LDEV failure occurs, the disk array suspends
disk arr
. If a PDEV failure occurs, BC pair status is not affected because of the
the pair
chitecture, but copy pace may be degraded.
RAID ar
Under certain conditions, BC volume pairs may need to be re-established.
1
Maximum number of pairs per disk array depends on installed firmware version.
Maximum number of pairs for the array
When you create BC pairs, resources called differential tables arerequired. Thenumberofdifferential
tables available in one disk array depends on the array's amount of shared memory for differential tables.
• You can use 13,652 differential tables if no additional shared memory for differential tables is
installed.
• You can use 30,718 differential tables if additional shared memory for differential tables is
installed.
NOTE:
Contact your HP account support representative for more information about adding additional
shared memory.
NOTE:
The maximum number of pairs you can create is 8,192, no matter how much shared memory for
differential tables is available. If a command device is installed in order to use RAID Manager, the
maximum number of pairs is 8,191 (when configuring pairs of 1 P-VOL: 1 S-VOL ratio).
To calculate the maximum number of BC pairs, you must calculate how many differential tables are
required to create BC pairs, and compare the result with the number of differential tables in the disk array.
llowing applications also use differential tables:
The fo
• ShadowImage for z/OS
• Hitachi FlashCopy Mirroring
Business Copy XP user guide
15
• Hitachi FlashCopy Mirroring version 2
• Flex Copy XP
• Auto LUN XP
• Snapshot XP
For more information, refer to the following documents:
• For ShadowImage for z/OS, Hitachi FlashCopy Mirroring, and Hitachi FlashCopy Mirroring
Version 2, see the HitachiShadowImageforz/OSuser guide.
• ForFlexCopyXP,see“CalculatingthemaximumnumberofFlexCopyXPcopypairs”.
• For Auto LUN XP, see “Calculating the number of Auto LUN XP concurrent migration plans”.
• ForSnapshotXP,seetheHP StorageWorks Snapshot XP user guide.
If BC is used in the same disk array as any of these applications, the number of available differential
tables for BC pairs is the number of differential tables in the disk array minus the number of differential
tables used by other applications.
If only BC uses differential tables, the following section describes how to calculate the number of
differential tables required for one BC pair, and the conditions you need to consider when calculating the
number of BC pairs that you can create.
NOTE:
You can use RAID Manager's inqraid command to query the number of differential tables required
when you create BC pairs. You can also use this command to query the number of unused differential
tables in the disk array. For more information about the inqraid command, see the
RAIDManagerXPuserguide
.
HP StorageWorks
Calculating the number of differential tables for one BC pair
When you create a BC pair, the number of required differential tables changes according to the
emulation type of the volumes. Use the equations in Table 3 to calculate the total number of differential
tables per pair.
16
Business Copy XP (BC) for the Array
Table 3 Total number of differential tables per pair
Emulation type
OPEN-3
OPEN-8
OPEN-9
OPEN-E
OPEN-L
OPEN-V
Equation
Total number of differential tables per pair = [(X ÷ 48) + (Y x 15)] ÷ Z
• (X): Volume capacity (KB)
1, 2
• (Y): Number of control cylinders associated with the emulation type (see Table 4)
• (Z): Number of slots that can be managed by a differential table (61,312)
NOTE:
Roundtheresultofthecalculationuptothenearestwholenumber.
For example, if the volume's emulation type is OPEN-3, and it is not a custom volume,
the volume capacity (X) is the default volume size, 2,403,360 KB, and total number of
differential tables is calculated as follows:
[(2,403,360÷48)+(8x15)]÷61,312=0.81860
Whenyouroundtothenearestwholenumber,theresultis1.Therefore,thetotal
number of differential tables for a pair is 1 when the emulation type is OPEN-3.
Totalnumberofdifferentialtablesperpair=(X÷256)÷(Z)
• (X): Volume capacity (KB)
2
• (Z): Number of slots that can be managed by a differential table (61,312)
NOTE:
Roundtheresultofthecalculationuptothenearestwholenumber.
For example, if the volume capacity (X) is the maximum OPEN-V volume capacity of
3,019,898,880 KB, the total number of differential tables is calculated as follows:
(3,019,898,880 ÷ 256) ÷ 61,312 = 192.40084
Whenyourounduptothenearestwholenumber,theresultis193. Therefore,thetotal
number of differential tables for a pair is 193 when the emulation type is OPEN-V.
1
If the selected volume is a CVS (custom volume size) volume, use the capacity of the custom volume instead of the default
volume capacity for the emulation type. Since the OPEN-L emulation type does not support custom volume operations,
you must use the default volume capacity of OPEN-L for X.
2
1KBequals1024bytes.
Table 4 Number of control cylinders according to emulation types
Emulation type
OPEN-3
OPEN-8
OPEN-9
OPEN-E
OPEN-L 7 (5,040 KB)
OPEN-V
Number of control cylinders
8(5,760KB
27 (19,440 KB)
19 (13 ,6 80
0(0KB)
)
KB)
Table 5 shows the relationship between emulation type, capacity, and differential tables. Table 6 shows
the number of differential tables used in OPEN-V.
Business Copy XP user guide
17
Table 5 Relationship between emulation type, capacity, and differential tables
Emulation type
OPEN-3
OPEN-9
OPEN-E
OPEN-L
OPEN-V
1
1GB=10243Bytes
Capacity
Does not depend on capacity
Up to 2.7GB
Up to 5.5GB 2
Up to 6.8GB 3
Up to 2.7GB
Up to 5.5GB 2
Up to 8.4GB
Up to 11.2GB
Up to 13.5GB
33.9GB 13
See Table 6
1
Differential tables per pair
1
1
1
3
4
5
Table 6 Number of differential tables used in OPEN-V
Capacity
1
Differen-
Capacity
tial tables
Up to 14.9GB
Up to 29.9GB 2 Up to 508.9GB
Up to 44.9GB
Up to 59.8GB
Up to 74.8GB
Up to 89.8GB 6 Up to 568.8GB 38
Up to 104.7GB
Up to 119.7GB 8 Up to 598.7GB
Up to 134.7GB
Up to 149.6GB
Up to 164.6GB
Up to 179.6GB 12 Up to 658.6GB
Up to 194.5GB
Up to 209.5GB
Up to 224.5GB
Up to 239.4GB
Up to 254.4GB
Up to 269.4GB
Up to 284.3GB
Up to 299.3GB 20 Up to 778.3GB 52 Up to 1,257.3GB
Up to 314.3GB
Up to 329.3GB 22 Up to 803.3GB
1
3Upto523.9GB35Upto1,002.8GB67
4
5
7
9Upto613.7GB
10 Up t o 628 .7 GB
11
13 U p t o 67 3 . 5 G B
14
15
16
17
18
19
21 Up to 793.3GB 53 Up to 1,272.3GB 85
Up to 493.9GB
Up to 538.8GB 36 Up to 1,017.8GB 68
Up to 553.8GB 37 Up to 1,032.8GB 69
Up to 583.7GB 39 Up to 1,062.7GB
Up to 643.6GB 43
Up to 688.6GB
Up to 703.5GB
Up to 718.4GB 48 Up to 1,197.4GB
Up to 733.4GB 49 Up to 1,212.4GB
Up to 748.4GB
Up to 763.4GB
1
Differen-
Capacity
1
tial tables
33 Up to 972.9GB 65
34
40
41
42
44
45
46
47
50
51
54
Up to 987.9GB 66
Up to 1,047.8GB
Up to 1,077.7GB 72
Up to 1,092.7GB 73
Up to 1,107.6GB
U p t o 1,12 2. 6 G B
U p t o 1,13 7. 6 G B 76
Up to 1,152.5GB
Up to 1,167.6GB 78
Up to 1,182.5GB 79
Up to 1,227.4GB
Up to 1,242.5GB
Up to 1,287.3GB 86
Differential tables
70
71
74
75
77
80
81
82
83
84
18
Business Copy XP (BC) for the Array
Capacity
1
Differen-
Capacity
tial tables
Up to 344.2GB
Up to 359.2GB
Up to 374.2GB
Up to 389.1GB 26 Up to 868.1GB 58
Up to 404.1GB
Up to 419.1GB
Up to 434.0GB
Up to 449.0GB
Up to 464.0GB
Up to 478.9GB
U p t o 1, 4 51. 9G B
Up to 1,466.9GB
Up to 1,481.8GB
Up to 1,496.8GB
Up to 1,511.8GB 101 Up to 2,005.8GB
Up to 1,526.8GB 102 Up to 2,020.7GB 135
Up to 1,541.7GB
Up to 1,556.7GB
Up to 1,571.7GB 105 Up to 2,065.6GB 138 Up to 2,559.6GB
Up to 1,586.6GB 106 Up to 2,080.7GB 139
Up to 1,601.6GB 107 Up to 2,095.6GB
Up to 1,616.6GB 108 Up to 2,110.5GB
Up to 1,631.5GB 109 Up to 2,125.5GB
Up to 1,646.5GB
Up to 1,661.5GB
Up to 1,67
Up to 1,691.4GB
Up to 1,706.4GB 114 Up to 2,200.4GB 147 Up to 2,694.3GB
Up to 1,7
Up to 1,736.3GB 116 Up to 2,230.3GB
Up to 1,751.3GB
Up to 1,766.3GB 118 Up to 2,260.2GB
Up to 1,781.2GB 119 Up to 2,275.2GB 152 Up to 2,769.2GB 185
Up to 1,796.2GB 120 Up to 2,290.2GB 153
Up to 1,
Up to 1,826.1GB 122 Up to 2,320.1GB
Up to 1,841.1GB
6.4GB
21.4GB
811. 2 GB
23 Up to 823.2GB
24
25 Up to 853.2GB
27 Up to 883.1GB 59 Up to 1,362.1G
28 Up to 898.1GB 60 Up to 1,377.1GB 92
29 Up to 913.0GB 61 Up to 1,392.0GB 93
30 Up to 928.0GB 62
31
32 Up to 957.9GB
97
9 8 U p t o 1,9 6 0 . 9 G B 131
99 Up to 1,975.8GB 132
100 Up to 1,990 .
103 Up to 2,035
104
110
111
11 2
11 3
11 5
11 7
121 U p t o 2 ,
123 Up to 2,335.1GB 156 Up to 2,829.0GB 189
Up to 838.2GB 56 Up to 1,317.2GB 88
Up to 943.0GB
Up to 1,945.9GB
Up to 2,050.7GB 137
Up to 2,140.5GB 143 Up to 2,634.4GB
Up to 2,155.4GB 144 Up to 2,649.4GB
Up to 2,17
Up to 2,185.4GB 146
Up to 2,215.3GB
Up to 2,245.3GB
1
8GB
.7GB
0.4GB
305.1GB
Differen-
Capacity
tial tables
55
57
63
64 Up to 1,436.9GB
13 0
13 3
13 4 U p t o 2 , 4 9 9. 7 G B
13 6 U p t o 2 , 5 2 9
14 0
141 Up to 2,604.5GB 174
14 2
14 5 U p t o 2 , 6 6
14 8
149 Up to 2,724.3GB
15 0 U p t o 2 ,7 39 . 2 G B 18 3
151
15 4
15 5
Up to 1,302.2GB 87
Up to 1,332.2GB 89
Up to 1,347.1GB
Up to 1,407.0GB 94
Up to 1,422.0GB
Up to 2,439.9GB
Up to 2,454.8GB 164
Up to 2,469.8GB
Up to 2,484.8GB
Up to 2,514.7GB
Up to 2,544.6GB
Up to 2,574
Up to 2,589.5GB 173
Up to 2,619.5GB
Up to 2,679.3GB 179
Up to 2,709.3GB 181
Up to 2,
Up to 2,784.1GB
Up to 2,
Up to 2,814.1GB
1
.7GB
.6GB
4.4GB
754.2GB
799.1GB
B
Differential tables
90
91
95
96
16 3
16 5
16 6
167
16 8
169
170
171
172
175
176
17 7
178
18 0
182
18 4
18 6
187
18 8
Business Copy XP user guide
19
Capacity
1
Differen-
Capacity
1
tial tables
Up to 1,856.1GB
Up to 1,871.0GB 125 Up to 2,365.0GB 158 Up to 2,859.0GB 191
Up to 1,886.0GB 126 Up to 2,380.0GB 159 Up to 2,873.9GB 192
Up to 1,901.0GB 127
Up to 1,915.9GB 128
Up to 1,930.9GB 129
1
1GB=10243Bytes
12 4
Up to 2,350.0GB
Up to 2,394.9GB
Up to 2,409.9GB
Up to 2,424.9GB
If you intend to create pairs with volumes of different emulation types, the maximum number of pairs you
can create depends on the following conditions.
NOTE:
For more information about calculating total number of differential tables per pair, see Table 3.
Calculating the number of BC pairs if LUSE is not used
Use the following equation to calculate whether the desired number of BC pairs can be created:
Σ{(α) x (number of BC Pairs)} ≤ (Β), where:
Differen-
Capacity
tial tables
15 7
16 0 U p t o 2 ,8 8 0 . 0 GB 19 3
161
16 2
Up to 2,844.0GB
1
Differential tables
19 0
Calculati
• (α) is the required number of differential tables per pair (see Table 3).
• (number of BC pairs) is the number of BC pairs you want to create.
• (Β) is number of differential tables in the disk array.
•(Β) = 13,652 when additional shared memory for differential tables is not installed.
•(Β) = 30,718 when additional shared memory for differential tables is installed.
For example, if you create 10 pairs of OPEN-3 volumes and 20 pairs of OPEN-V volumes in a disk array
that does not have additional shared memory for differential tables, use the following equation:
1x10+193x20=3870≤ 13 , 652
Since 3,870 is less than 13,652, 10 pairs of OPEN-3 volumes and 20 pairs of OPEN-V volumes can
be created.
NOTE:
When the emulation type is OPEN-3, and the capacity of the volume is 2,403,360 KB, the number of
differential tables required for a pair is 1. When the emulation type is OPEN-V, and the capacity of the
volume is 3,019,898,880 KB, the number of differential tables required for a pair is193.
ng the number of BC pairs if LUSE is used
Use the fol
Σ[Σ{(α)x(
lowing equation to calculate whether the desired number of BC pairs can be created:
number of volumes that form LUSE volumes)} x (number of BC pairs)] ≤ (Β), where:
• (α) is the required number of differential tables for each volume that forms the LUSE volume.
When you use LUSE volumes to create a BC pair, every volume that forms the LUSE volume uses the
differen
created b
tial tables as a pair. For example, if you create a BC pair by using LUSE volumes that are
y combining two OPEN-V volumes, you need differential tables for two OPEN-V pairs.
• (Β) is number of differential tables in the disk array.
•(Β) = 13,652 when additional shared memory for differential tables is not installed.
20
Business Copy XP (BC) for the Array
•(Β) = 30,718 when additional shared memory for differential tables is installed.
For example, if you create 10 pairs of LUSE volumes consisting of three OPEN-3 volumes, use the
following equation:
(1x3)x10=30≤ 13 , 6 5 2
Since 30 is less than 13,652, 10 pairs of LUSE volumes consisting of three OPEN-3 volumes can
be created.
NOTE:
WhentheemulationtypeisOPEN-3,andthecapacityofthevolumeis2,403,360KB,thenumberof
differential tables required for a pair is 1.
BC operations
Set reserve attribute operation
This operation reserves a volume so it can be used as a BC S-VOL. Reserved volumes can only be used as
BC S-VOLs. The disk array rejects all write operations to reserved volumes (unless in split (PSUS) status or
PSUS(SP)).Youcanreserveupto4,095volumesinonediskarray.UsetheSetReserveAttributewindow
(see Setting reserve attributes) to reserve volumes for use as BC S-VOLs.
A volume might be reserved for BC to ensure that a server does not mount it before BC can use it in a
pair. BC cannot use a volume as an S-VOL if it is being used by a server.
NOTE:
BC leaf volumes (L2 cascade pair) also function as S-VOLs and must be reserved prior to being assigned
to an L2 cascade pair.
Reset reserve attribute operation
This operation unreserves a volume so it can be mounted and accessed by all hosts. After you reset the
reserve attribute, the disk array accepts all subsequent I/O operations to the volume. Use the Reset
Reserve Attribute window (see Resetting reserve attributes) to unreserve volumes.
Paircrea
te operation
This operation establishes the new BC pairs. The volume that will be the P-VOL must be in the SMPL
(simplex)state,andthevolumethatwillbetheS-VOLmustbeintheSMPLstatebeforebeingaddedto
a BC pair.
NOTE:
You can reserve the S-VOL before creating a pair, but you can also create a pair with an unreserved
S-VOL. Use the Paircreate window (see Creating BC pairs (Paircreate)) to create new BC volume pairs.
Initial copy operation
This operation occurs when you create a new volume pair (see Figure 2). The BC initial copy operation
copies all data on the P-VOL to the associated S-VOL. The P-VOL remains available to all hosts for read
and write I/Os throughout the initial copy operation. After the initial copy is complete, the update
copy operation duplicates write operations performed on the P-VOL during the initial copy operation at
the S-VOL.
Business Copy XP user guide
21
Before the initial copy operation, the status of a pair is SMPL. The status of the pair is COPY(PD)
(PD = pending) while the initial copy operation is in progress. The status changes to PAIR when the
initial copy is complete. Write operations performed on the P-VOL during the initial copy operation are
duplicated at the S-VOL by update copy operations after the initial copy is complete.
CAUTION:
Even if a copy operation is completed without any host I/O, the data in the P-VOL and S-VOL may not
beidentical.WhethertheP-VOLandtheS-VOLhavethesamedatadependsontheconditionofthe
disk array. To make the P-VOL and S-VOL data the same, split the pair and make the pair status PSUS.
NOTE:
When creating pairs, you can select the pace for the initial copy operation: slower, medium, and faster.
TheslowerpaceminimizestheimpactofBCoperationsondiskarrayI/Operformance,whilethefaster
pace completes the initial copy operation as quickly as possible.
Figure 2 Adding a pair in BC
Update copy operation
This operation updates the S-VOL of a BC pair after the initial copy operation is complete. Since a P-VOL
remains available to all hosts for read and write I/Os during the initial copy operation, the P-VOL might
be updated during the operation. Therefore, when the status of the pair changes to PAIR after the
initial copy operation is complete, the update copy operation takes place and the P-VOL's differential
s copied to the S-VOL. Update copy operations take place only for duplex pairs (status = PAIR).
data i
As write I/Os are performed on a duplex P-VOL, the disk array stores a map of the P-VOL's differential
data, and performs update copy operations periodically based on the amount of differential data present
P-VOL and the elapsed time between update copy operations. Figure 3 illustrates an update
on the
copyoperationinaBCpairwithonlyoneS-VOL.
22
Business Copy XP (BC) for the Array
CAUTION:
Even if a copy operation is completed without any host I/O, the data in the P-VOL and S-VOL may not
beidentical.WhethertheP-VOLandtheS-VOLhavethesamedatadependsontheconditionofthe
disk array. To make the P-VOL and S-VOL data the same, split the pair and make the pair status PSUS.
NOTE:
• Update copy operations are not performed for pairs with the following status: COPY(PD) (
), COPY(SP) (
duplex
resync
), COPY(RS-R) (
(
• Update copy operations do not occur every time a host issues a write I/O operation to the P-VOL of
a BC pair. BC update copy operations are performed asynchronously according to the differential
bitmap, which is stored in shared memory.
• If shared memory is lost (for example, offline micro exchange or volatile PS on), the differential
bitmap is also lost. In this case, the disk array treats the entire BC P-VOL (S-VOL for COPY(RS) pairs)
as difference data and recopies all data to the S-VOL (P-VOL for COPY(RS) pairs) to ensure proper
pair resynchronization. For pairs with COPY(SP) or PSUS(SP) status, the disk array changes the status
to PSUE due to the loss of the differential bitmap, also ensuring proper resynchronization of these
pairs. If shared memory is lost, allow extra time for BC operations.
steady split pending
resync-reverse
), and PSUE (
), PSUS(SP) (
suspended
quick split pending
).
), PSUS (
split)
pending
,COPY(RS)
Figure 3 Update copy operation
Cascade function
This function creates a second layer of BC volume pairs (L2) underneath the first layer of BC pairs (L1).
Cascade
BC pair
Cascad
s(Paircreate)). This cascade layering scheme creates up to nine copies of one BC P-VOL. See
efunctionfor further information on cascade pairs and the cascade function.
Pairsplit operation
The BC split capability, by making the BC copies (S-VOLs) available for host access, provides a
point-in-time copy that can be used for data backup or to provide real data for test purposes. The BC
pairsplit operation copies all P-VOL data or differential data to the S-VOL to make the S-VOL identical to
theP-VOL.IftherearealotofhostI/OsfortheP-VOL,itmighttakelongertosynchronizetheP-VOL
and S-VOL.
Use the Pairsplit window to split existing BC pairs or to add and split new BC pairs in one step. When
you split an existing pair, only the differential data is copied to the S-VOL. When you create and split a
pairs are created by clicking Cascade instead of Set in the Paircreate window (see Creating
Business Copy XP user guide
23
Copy pace
Split type
new pair, all P-VOL data is copied to the S-VOL. When the split operation is complete, the pair status
changes to PSUS, and you have full read/write access to the split S-VOL (even though it is still reserved).
While the pair is split, the disk array establishes a track map for the split P-VOL and S-VOL, and
records a list of the changed tracks for both volumes. The P-VOL remains fully accessible during the
pairsplit operation, and the accessibility of the S-VOL depends on the split type (see Split type). Pairsplit
operations cannot be performed on suspended (PSUE, COPY(RS), or COPY(RS-R)) pairs.
When splitting pairs, you can select the pace for the pending update copy operation: Slower, Medium,
and Faster. The slower pace minimizes the impact of BC operations on disk array I/O performance,
while the fas
When splitting pairs, you can select the split type: Quick Split or Steady Split.
• When you specify Quick Split, the pair status changes to PSUS(SP), and the S-VOL is available
immediately for read and write I/Os (even though it is still reserved). All P-VOL data or differential
data is copied to the S-VOL in the background.
• When you specify Steady Split, the pair status changes to COPY(SP), and all P-VOL data or
differential data is copied to the S-VOL. When the operation is complete, the pair status changes
toPSUS,andyouhavefullread/writeaccesstothesplitS-VOL(eventhoughitisstillreserved).
If you want to finish the copy operation quickly in order to access the S-VOL, take the P-VOL
offline before performing the operation.
ter pace splits the pairs as quickly as possible.
NOTE:
Refer to the Table 7 for information about read/write operations from host servers to P-VOLS and
S-VOLS of BC pairs during a pairsplit operation.
Pairresync operations
To change the status of the pairs from PSUS to PAIR, or from PSUE to PAIR, you must resynchronize the
pairs. BC can perform the following types of pairresync operations according to the speed and direction
of the resynchronization:
• Normal Copy
• Quick Resync
• Reverse Copy
• Quick Restore
Use the Pairresync pane to resynchronize split and suspended BC pairs. When the pairresync operation
starts, the pair status changes to COPY(RS) or COPY(RS-R). When the pairresync is complete, the pair
status changes to PAIR. The local disk array resumes BC update copy operations after the pair status
changes to PAIR. The P-VOL remains fully accessible during a normal pairresync operation, but is
inaccessible to all hosts during a reverse or quick restore pairresync operation. This ensures that data
on the P-VOL is identical to data on the S-VOL when the reverse or quick restore pairresync operation
completes.
NOTE:
You can use BC to perform normal or quick pairresync operations on split and suspended pairs, but you
can perform reverse or quick restore pairresync operations only on split pairs.
24
Business Copy XP (BC) for the Array
Forward pairre
sync operation
A forward pairr
are the types o
• Normal.Thisoperation(seeFigure 4) resynchronizes the S-VOL with the P-VOL. The copy
direction for a normal pairresync operation is P-VOL to S-VOL. The pair status during a normal
resync operation is COPY(RS), and the P-VOL remains accessible to all hosts for read and write
operations during a normal pairresync.
• Quick.This
data to the S-VOL. The P-VOL and S-VOL are resynchronized when update copy operations are
performed for duplex pairs (status = PAIR). The pair status during a quick pairresync operation
is PSUS(SP) until the differential map is copied, and the P-VOL remains accessible to all hosts
for read an
pairresync operation.
esync operation resynchronizes pairs by copying data on P-VOLs to S-VOLs. The following
f forward pairresync operations:
operation speeds up the normal pairresync operation without copying the P-VOL
d write operations. The S-VOL becomes inaccessible to all hosts during a quick
re 4 Normal and quick pairresync operations
Figu
CAUTION:
Even if a copy operation is completed without any host I/O, the data in the P-VOL and S-VOL may not
beidentical.WhethertheP-VOLandtheS-VOLhavethesamedatadependsontheconditionofthe
array. To make the P-VOL and S-VOL data the same, split the pair and make the pair status PSUS.
disk
Backward pairresync operation
A backward pairresync operation resynchronizes pairs by copying data on S-VOLs to P-VOLs. The
following are the types of backward pairresync operations:
Business Copy XP user guide
25
• Reverse. This operation (see Figure 5) synchronizes the P-VOL with the S-VOL. The copy direction
for a reverse pairresync operation is S-VOL to P-VOL. Table 7 shows the requirements for reverse
and quick restore pairresync operations. If you perform these operations on pairs that do not
meet the requirements, the reverse copy or quick restore command is rejected. The pair status
during a reverse resync operation is COPY(RS-R), and the P-VOL and S-VOL become inaccessible
to all hosts for write operations during a reverse pairresync operation. When the reverse
pairresync is complete, the P-VOL becomes accessible. The reverse pairresync operation can only
be performed on split pairs (PSUS status), not on suspended pairs (PSUE status). The reverse
pairresync operation cannot be performed on L2 cascade pairs.
NOTE:
The P-VOL remains read-enabled during the reverse pairresync operation only to enable the host to
recognize the volume. Data on the P-VOL is not guaranteed until the reverse pairresync operation is
complete and the status changes to PAIR.
• Quick Restore.Thisoperation(Figure 5) speeds up reverse resync by changing the volume map in
the disk array to swap the contents of the P-VOL and S-VOL without copying the S-VOL data to the
P-VOL. The P-VOL and S-VOL are resynchronized when update copy operations are performed
for pairs in PAIR status. The pair status during a quick restore operation is COPY(RS-R) until the
volume map change is complete. The P-VOL and S-VOL become inaccessible to all hosts for write
operations during a quick restore operation. Quick restore cannot be performed on L2 cascade
pairs or on suspended pairs (PSUE status). Table 7 shows the requirements for reverse and quick
restore pairresync operations. If you perform these operations on pairs that do not meet the
requirements, the reverse copy or quick restore command is rejected.
26
Business Copy XP (BC) for the Array
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