Hitachi TrueCopy for IBM z/OS User and Reference Guide (T5211-96001, June 2007)

5-62 Performing TrueCopy for z/OS Configuration Operations
Hitachi Universal Storage Platform V TrueCopy for IBM z/OS User’s Guide
Table 5-7 Optimizing TrueCopy for z/OS Operations and USP V
Performance
Condition Description Recommendation(s)
Write-intensive
workloads
Write-intensive workloads, such as SPOOL
volumes and database logging volumes, can have
a significant impact on storage system I/O
response times.
Spread write-intensive data across several
volumes to minimize queuing.
Large block size
Workloads with large write block sizes, such as
DB2 deferred writes, can impact performance.
Spread workloads with large write block
sizes across several volumes.
High host channel
demand
The demand on the MCU’s host channels can
affect performance.
Spread the workload across several
storage systems to utilize additional
channels.
Sequential write
operations
TCz operations can have a negative impact on
workloads with a high percentage of sequential
write operations, such as batch processing
operations (e.g., dump/restore, sort operations).
Avoid performing restore operations to
volumes which belong to TCz pairs.
Instead, restore data to a scratch volume
and then establish the TCz pair.
Cache size
Large cache size improves read hit performance,
which allows more storage system resources to
be devoted to write operations. The resulting
performance improvement can offset some or all
of the performance loss due to the TCz remote
copy operations.
TCzA and Concurrent Copy (CC) require additional
cache for sidefile data. Insufficient cache resources
can result in command retries, SCP notifications, and
puncture conditions.
Consider increasing the cache size of the
TCz storage systems to handle TCzA and
CC sidefile operations and to improve
overall storage system performance. For
best results, the cache and NVS capacity of
the main and remote storage systems
should be the same (for TCzA the RCU
sidefile requirements are 2x that of the
MCU) to enable the remote site to function
adequately during disaster recovery.
RCU capacity
The performance of the RCUs directly affects the
performance of the MCUs. If an RCU becomes
overloaded with heavy update activity, MCU and
system performance can also be degraded.
Distribute TCz remote copy operations
among several remote storage systems to
avoid overloading any one RCU.
Remote copy
connection paths
An inadequate number of remote copy connection
paths may decrease storage system
performance. Performing TCz Synchronous
operations over long distances can also degrade
storage system performance. TCzA is
recommended for long distances.
Make sure to install an adequate number
of remote copy connection paths between
the main and remote storage systems.
This is especially important for storage
systems which contain both M-VOLs and
R-VOLs.