Controlling Over-Provisioning of Your Storage Ports

Best Practices, latency, over-provisioning, SAN, storage arrays, VirtualWisdom No Comments »

While it’s generally accepted that SAN storage utilization is low, only a few industry luminaries, such as John Toigo, have talked about the severe underutilization of Fibre Channel (FC) SAN fabrics.  The challenge, of course, is that few IT shops have actually instrumented their SANs to enable accurate measurements of fabric utilization.  Instead, 100% of enterprise applications get the bandwidth that perhaps only 5% of the applications, wasting CAPEX need. 

In dealing with several dozen large organizations, we have found that nearly all FC storage networks are seriously over-provisioned, with average utilization rates well below 10%.  Here’s a VirtualWisdom dashboard widget (below) that shows the most heavily utilized storage ports on two storage arrays, taken from an F500 customer.  The figures refer to “% utilization.”

Beyond the obvious unnecessary expense, the reality is that with such low utilization rates, simply building in more SAN hardware to address performance and availability challenges does nothing more than add complexity and increase risk.  With VirtualWisdom, you can consolidate your ports, or avoid buying new ones, and track the net effect on your application latency to the millisecond.  The dashboard widgets below show the “before” and “after” latency figures that resulted from the configuration changes to this SAN, using VirtualWisdom.  They demonstrate a negligible effect.

Latency “before”

Latency “after”

Our most successful customers have tripled utilization and have been able to reduce future storage port purchases by 50% or more, saving $100 – $300K per new storage array.

For a more detailed discussion of SAN over-provisioning, click here, or check out this ten-minute video discussing this issue and over-tiering.

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