Monday, 23 February 2015

Performance Capacity – Response Impacts - Key Metrics for Effective Storage Performance and Capacity Reporting (7 of 10)

SAN or storage array performance problems can be identified at the host or backend storage environment.
The diagram below shows a typical performance impact in the more complex environment.

With SAN attached storage you can share storage across multiple servers, one of the downsides of this is that you can have storage response impact across multiple servers too.

Performance Capacity – Host Metrics

It is important that you understand the limitations of certain host metrics.
A selection of host metrics are shown below:

       Measured response is the best metric for identifying trouble.

       Host utilization only shows busy time, it doesn’t give capacity for SAN.

       Physical IOPs is an important measure of throughput, all disks have their limitation.

       Queue Length is a good indicator that a limitation has been reached somewhere.

Performance Capacity – Host Metrics

Metrics like host utilization can indicate impactful events, but ample capacity might still be available.

The high utilization can be seen generating large amounts of I/O in the chart below.

Queue lengths indicate that it may not currently be impacting response, but headroom is unknown. Response time is the key, as users will be impacted if it goes up.

Next time I’ll look at array architecture. 
If you missed our recent webinar on Storage performance sign up for our Community and download or listen for free

Dale Feiste
Principal Consultant

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