HP StorageWorks XP Remote Web Console Software - Manual (Page 33)

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XP Continuous Access pairs and Hitachi TrueCopy for z/OS pairs cannot be intermixed in a
consistency group.
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If you specify a consistency group for XP Continuous Access Asynchronous pair, only XP
Continuous Access Asynchronous pairs that belong to the same CLPR can be allocated to one
XP Continuous Access consistency group. For more information about CLPRs, see the
HP StorageWorks XP Disk/Cache Partition user guide for XP12000/XP10000 Disk Arrays
and SVS200.
Accessing XP Continuous Access P-VOLs and S-VOLs
To ensure maximum data integrity during normal XP Continuous Access operations, the RCU rejects
all write operations issued by a host to an XP Continuous Access S-VOL. If you need write access
to an XP Continuous Access S-VOL, split the pair using the S-VOL write option (see
“S-VOL write
option” (page 17) ). When you resume (resync) the split pair, the RCU sends the S-VOL cylinder
bitmap to the MCU to ensure proper resynchronization of the pair.
Cache and nonvolatile storage (NVS)
Cache and nonvolatile storage (NVS) must be operable for both the MCU and RCU of an XP
Continuous Access volume pair. If not, the XP Continuous Access paircreate operation fails.
Configure the remote disk array cache to adequately support XP Continuous Access remote copy
workloads and local workload activity.
NOTE: NVS is the portion of cache with a battery backup.
Host failover software
Host failover software is a critical component of any disaster recovery effort. When an MCU fails
to maintain synchronization of an XP Continuous Access pair, the MCU generates sense information.
This information must be transferred to the remote site via the host failover software for effective
disaster recovery.
Duplicate volumes
Because the contents of the P-VOL and S-VOL of an XP Continuous Access pair are identical, the
S-VOL is considered a duplicate of the P-VOL. Because the host operating system does not allow
duplicate volumes, the host system administrator must take precautions to prevent system problems
related to duplicate volumes. You must define the XP Continuous Access S-VOLs so they do not
auto-mount or come online to the same host at the same time as the P-VOLs (see the following
CAUTION).
Requirements and restrictions 33