Administrator Guide

• The background monitoring process samples and stores data for a seven-day time period. If a monitored object changes during this
time, the object does not have a complete set of data points spanning the full seven days. For example, virtual disk sets can change as
virtualDisks are created, deleted, mapped, or unmapped or physical disks can be added, removed, or failed.
• Performance data is collected and displayed only for an I/O host visible (mapped) virtual disk, a snapshot group repository virtual disk,
and a consistency group repository virtual disk. Data for a replication repository virtual disk is not collected.
• The values reported for a RAID controller module or storage array might be greater than the sum of the values reported for all the
virtual disks. The values reported for a RAID controller module or storage array include both host I/Os and I/Os internal to the storage
array (metadata reads and writes), whereas the values reported for a virtual disk include only host I/O.
Interpreting performance monitor data
Performance Monitor provides you with data about devices. You can use this data to make storage array performance tuning decisions, as
described in the following table:
Table 4. Performance data implications
Performance Data Implications for Performance Tuning
Total I/Os This data is useful for monitoring the I/O activity of a specific RAID
controller module and a specific virtual disk, which can help identify
possible high-traffic I/O areas.
You might notice a disparity in the total I/Os (workload) of RAID
controller modules. For example, the workload of one RAID
controller module is heavy or is increasing over time while that of
the other RAID controller module is lighter or more stable. In this
case, you might want to change the RAID controller module
ownership of one or more virtual disks to the RAID controller
module with the lighter workload. Use the virtual disk total I/O
statistics to determine which virtual disks to move.
You might want to monitor the workload across the storage array.
Monitor the Total I/Os in the background performance monitor. If
the workload continues to increase over time while application
performance decreases, you might need to add additional storage
arrays. By adding storage arrays to your enterprise, you can
continue to meet application needs at an acceptable performance
level.
IOs/sec
Factors that affect input/output operations per second (IOs/sec
or IOPS) include these items:
• Access pattern (random or sequential)
• I/O size
• RAID level
• Cache block size
• Whether read caching is enabled
• Whether write caching is enabled
• Dynamic cache read prefetch
• Segment size
• The number of physical disks in the disk groups or storage
array
The transfer rates of the RAID controller module are determined by
the application I/O size and the I/O rate. Generally, small
application I/O requests result in a lower transfer rate but provide
a faster I/O rate and shorter response time. With larger application
I/O requests, higher throughput rates are possible. Understanding
your typical application I/O patterns can help you determine the
maximum I/O transfer rates for a specific storage array.
You can see performance improvements caused by changing the
segment size in the IOPS statistics for a virtual disk. Experiment to
determine the optimal segment size, or use the file system size or
About your MD Series storage array
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