Tuesday, 25 September 2012

Troubleshooting excessive I/O on a LUN in VMware


If you notice a lot of I/O being generated on a particular LUN. How do you figure out who / what is causing this? Well it is not as difficult as you think it would be…
  • Open up esxtop
  • Go to the “Device” view (U)
  • Find the device which is causing a lot of I/O
  • Press “e” and enter the “Device ID” in my case that is an NAA identifier so “copy+paste” is easiest here
  • Now look up the World ID under the “path/world/partition” column
  • Go back to CPU and sort on %USED (press “U”)
  • Expand (press “e”) the world that is consuming a lot of CPU, as CPU is needed to drive I/O

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