HP XP P9500 Storage - Manual (Page 14)

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