HP XP Continuous Access Software - Manual (Page 77)

Continuous Access XP user guide for the XP1024/XP128 77
Discontinuing Continuous Access XP operations
If you plan to use Continuous Access XP for nondisruptive data migration or duplication (see ” Using
Continuous Access XP for data migration and duplication ” on page 94), configure and establish
Continuous Access XP operations, allow Continuous Access XP to synchronize volumes, redirect
application I/Os (if migrating), and discontinue Continuous Access XP operations. When you are ready
to discontinue Continuous Access XP operations, perform Continuous Access XP operations in the correct
order to avoid error messages. For example, Continuous Access XP will not delete an RCU path until you
delete all Continuous Access XP pairs still using that path, and you cannot delete a group until you delete
all Continuous Access XP Asynchronous pairs in that group.
1. Delete all Continuous Access XP pairs from MCUs (pairsplit-S, see ” Deleting Continuous Access XP
volume pairs (Pairsplit-S) ” on page 90). For Continuous Access XP Async pairs, use the Delete
Range-Group option to delete all pairs in a group at one time. Verify that the pair status changed to
SMPL for all Continuous Access XP volumes before continuing.
2. Delete Continuous Access XP Async groups from MCUs (see ” Deleting consistency groups (Delete CT
Group) ” on page 70). The RCU automatically deletes a group when all pairs in the group are deleted.
3. Delete RCUs (see ” Deleting RCUs (Delete RCU) ” on page 61). Check each CU image of each MCU to
ensure that all RCUs are deleted before continuing.
4. Remove remote copy connections (physical paths). If you are not familiar with the operation of remote
copy hardware components, call HP technical support for assistance.
Sequential write
operations
Continuous Access XP operations can
have a negative impact on workloads with a
high percentage of sequential write
operations, such as batch processing
operations (for example, dump/restore, sort
operations).
Avoid performing restore operations to
volumes belonging to
Continuous Access
XP pairs. Instead, restore data to a scratch
volume and then create the Continuous
Access XP volume pair.
Cache size Large cache size improves read hit
performance, which allows more disk array
resources to be devoted to write operations.
Resulting performance improvements can
offset some or all performance losses due to
Continuous Access XP remote copy
operations.
Continuous Access XP Asynchronous
requires additional cache for sidefile data.
Insufficient cache resources can result in
command retries, state-change-pending
(SCP) notifications, and puncture conditions.
Consider increasing cache size of
Continuous Access XP disk arrays to
handle cache sidefile operations and
improve overall disk array performance. For
best results, cache and NVS capacity of
primary and secondary disk arrays should
be the same (for
Continuous Access XP
Asynchronous, RCU sidefile requirements
are twice that of the MCU) to enable the
remote site to function adequately during
disaster recovery.
RCU capacity Performance of RCUs directly affects
performance of MCUs. If an RCU is
overloaded with heavy update activity,
MCU and system performance can also be
degraded.
Distribute Continuous Access XP remote
copy operations among several remote disk
arrays to avoid overloading any one RCU.
Paths An inadequate number of paths may
decrease disk array performance.
Performing
Continuous Access XP
Synchronous operations over long distances
can also degrade performance.
Continuous Access XP Asynchronous is
recommended for long distances.
Ensure an adequate number of paths
between the primary and secondary disk
arrays are installed. This is especially
important for disk arrays containing both
P-VOLs and S-VOLs.
Table 18 Disk array performance conditions and recommendations (continued)
Condition Description Recommendations