HP XP7 Storage - Manual (Page 29)

NOTE: Neither cache nor shared memory can be added to or removed from the storage system
when pair status is Pending. When either of these tasks is to be performed, first split any pairs in
Pending status; then resynchronize the pairs when the cache or shared memory operation is
completed.
DASD fast write requirements
DASD fast write (DFW) is required at the primary and secondary system only when Required is
specified for the PPRC DFW to S-VOL option. If DFW to an S-VOL is blocked, but the pair was
established with the Required option specified, the primary system detects DFW OFF at the S-VOL
and splits the pair. The default for Continuous Access Synchronous Z pairs created using PPRC
commands is Not Required, therefore they are not split when DFW to S-VOL is blocked.
The DFW to S-VOL setting does not affect P-VOL I/O performance. If one side of cache is closed
due to a secondary system failure, the copy operation still uses DFW. The difference between not
required and required is that new pairs cannot be established with the required option when one
side of RCU cache is closed. In this case, the Add Pair operation fails (This restriction applies only
when the CU emulation type of RCU is 3390).
Requirements for XP7 with earlier model storage systems
You can pair XP7 volumes with P9500 and XP24000/XP20000 Disk Array volumes. However, if
the XP7 volumes are in a consistency group consisting of multiple XP7 systems, XP24000/XP20000
Disk Array cannot be used. In this case, all paired volumes must belong to XP7 or P9500.
•
When connecting XP7 with P9500 or XP24000/XP20000 Disk Array, contact your HP
representative for information regarding the supported microcode versions.
•
When using the previous model storage system at the remote site, make sure the primary and
secondary system have unique serial numbers.
NOTE: When using RAID Manager (or Raidcom), the XP7 serial number requires a prefix
of "3".
S-VOL Read and other system options
You can tailor XP7 storage systems to enable the S-VOL Read option and other functions. System
option modes related to Continuous Access Synchronous Z and PPRC operations are shown in the
following table.
(For more information about I/O to the S-VOL, see “About allowing I/O to the S-VOL” (page 36) .)
XP7 option modes are set to their default values at installation, and can be changed only by your
HP representative.
Description Option mode
S-VOL read-only function (secondary system only). 20
Selects function of CRIT=Y(ALL) or CRIT=Y(PATHS): 36
•
ON: CRIT=Y(ALL) => equivalent to Fence Level = Data.
• OFF: CRIT=Y(PATHS) => equivalent to Fence Level = Status.
Allows you to change the volume that is split when the FREEZE command is issued from the host. The
target will change from the volume in the CU for which the FREEZE command is issued to the volume
in the entire DKC if this mode is ON: 64
•
ON: The volume in the entire DKC is split.
• OFF: The volume in the CU for which the FREEZE command is issued is split.
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