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Troubleshooting Storage Performance in vSphere

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When we troubleshoot performance related issues, the first think which would hit our mind it "Storage". So let's have a sneak peak about the basic troubleshooting of the storage related issues. 
Poor storage performance is generally the result of high I/O latency. vCenter or esxtop will report the various latencies at each level in the storage stack from the VM down to the storage hardware.  vCenter cannot provide information for the actual latency seen by the application since that includes the latency at the Guest OS and the application itself, and these items are not visible to vCenter. vCenter can report on the following storage stack I/O latencies in vSphere.
 Storage Stack Components in a vSphere environment
GAVG (Guest Average Latency) total latency as seen from vSphere KAVG (Kernel Average Latency) time an I/O request spent waiting inside the vSphere storage stack.  QAVG (Queue Average latency) time spent waiting in a queue inside the vSphere Storage Stack. DAVG…