HP StorageWorks XP Remote Web Console Software User Manual
Page 93
In addition to XP Continuous Access update copy mode, several other factors can also affect disk
array performance. You can optimize XP Continuous Access operations and I/O performance of
disk arrays by analyzing workloads and addressing system-level conditions (for example, number
of Fibre Channel paths) that can affect disk array performance. You can also control the impact
of XP Continuous Access operations on disk array performance by selecting the appropriate RCU
options for each MCU (see
and
) and the appropriate update copy mode (synchronous or asynchronous) and pair
options (see
“Creating XP Continuous Access volume pairs (Paircreate)” (page 99)
) for each XP
Continuous Access pair. In addition, you can upgrade XP Continuous Access hardware components
and adjust the configuration of components to improve disk array performance under a wide range
of operating conditions.
lists conditions affecting disk array performance and provides recommendations
for addressing these conditions.
Table 27 Disk array performance conditions and recommendations
Recommendations
Description
Condition
Spread write-intensive data across several
volumes to minimize queuing. Also consider
increasing the duplex write line (DWL) of the
disk array using Performance Advisor XP
(Performance Advisor XP running at the same
time is not supported).
Write-intensive workloads, such as database
logging volumes, can have a significant impact
on disk array I/O response times.
Write-intensive
workloads
Spread workloads with large write block sizes
across several volumes.
Workloads with large write block sizes, such
as DB deferred writes, can impact
performance.
Large block size
Spread workloads across several disk arrays
to utilize additional channels.
Demand on MCU's host channels can affect
performance.
High host channel
demand
Avoid performing restore operations to volumes
belonging to XP Continuous Access pairs.
Instead, restore data to a scratch volume and
then create the XP Continuous Access volume
pair.
XP Continuous Access 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).
Sequential write
operations
Consider increasing cache size of XP
Continuous Access 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 XP Continuous
Access Asynchronous, RCU sidefile
requirements are twice that of the MCU) to
enable the remote site to function adequately
during disaster recovery.
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 XP
Continuous Access remote copy operations.
XP Continuous Access Asynchronous requires
additional cache for sidefile data. Insufficient
cache resources can result in command retries,
state-change-pending (SCP) notifications, and
puncture conditions.
Cache size
Distribute XP Continuous Access remote copy
operations among several remote disk arrays
to avoid overloading any one RCU.
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.
RCU capacity
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.
An inadequate number of paths may decrease
disk array performance. Performing XP
Continuous Access Synchronous operations
over long distances can also degrade
performance. XP Continuous Access
Asynchronous is recommended for long
distances.
Paths
Optimizing XP Continuous Access operations and disk array performance
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