HP XP7 Storage - Manual (Page 27)

Planning pair volumes
The following information can help you prepare volumes for configuration. Also, see system
requirements and specifications in
“Requirements and specifications” (page 16) for more information.
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The emulation and capacity for the S-VOL must be the same as for the P-VOL
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When the S-VOL is connected to the same host as the P-VOL, the S-VOL must be defined to
remain offline.
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CU emulation type I-2107 must be used for primary and secondary systems.
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CU emulation type I-2107 is required for SMS I/O time stamping of Cnt Ac-J Z journals.
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When creating multiple pairs in the same operation, make sure that you set up S-VOL LDEVs
in a way that allows the system to correctly match them to selected P-VOLs.
Even though you select multiple volumes as P-VOLs in the Remote Web Console Create Pairs
procedure, you are able to specify only one S-VOL. The system automatically assigns LDEVs
on the secondary system as S-VOLs for the other selected P-VOLs according to LDEV.
You will have two options for specifying how the system matchs S-VOLs to P-VOLs.
- Interval: The interval you specify will be skipped between LU numbers in the secondary
system.
For example, suppose you specify LDEV 01 as the initial (base) S-VOL, and specify 3 for
Interval. This results in secondary system LU 04 being assigned to the next P-VOL, 07 assigned
to the subsequent P-VOL, and so on. To use Interval, you set up secondary system LU numbers
according to the interval between them.
- Relative Primary Volume. The difference is calculated between the LDEV numbers of two
successive P-VOLs. S-VOLs are assigned according to the closest LDEV number.
For example, if the LDEV numbers of three P-VOLs are 01, 05, and 06; and you set LDEV
numbers for the initial S-VOL (Base Secondary Volume) at 02, the LDEV numbers of the three
S-VOLs will be set at 02, 06, and 07, respectively.
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You can create a Cnt Ac-J Z pair using a Continuous Access Synchronous Z initial copy, which
takes less time. To do this, system option 474 must be set on the primary and secondary
systems. Also, a script is required to perform this operation. For more on system option 474
and how to do this operation, see
“System option modes ” (page 37) .
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Cnt Ac-J Z supports the Virtual LVI feature, which allows you to configure custom LDEVs that
are smaller than standard LDEVs. When custom LDEVs are assigned to a Cnt Ac-J Z pair, the
S-VOL must have the same capacity as the P-VOL. For details about Virtual LVI feature, see
the HP XP7 Provisioning for Mainframe Systems User Guide.
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Identify the volumes that will become the P-VOLs and S-VOLs.
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You can create multiple pairs at the same time. Review the prerequisites and steps in “Creating
the Cnt Ac-J Z initial copy ” (page 68) .
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When you create a Cnt Ac-J Z pair, you will have the option to create only the relationship,
without copying data from P-VOL to S-VOL. You can use this option only when data in the two
volumes is identical.
Data and journal volume specifications
The following table shows maximum capacities and volume types that can be used for data volumes
and journal volumes.
Planning pair volumes 27