Viewaskew
Enthusiast
Enthusiast

Disk latency data counters. Where can I find them?

I’m trying to view the below counters on an ESXi5 host and the link below advises that I should be able to view these from the Performance Advance Charts to view but under this view under Disk the only counters are Highest Latency (as well as Usage, Read rate & Write rate).

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Anyone know where I can view these counters so I can see if my results are within the recommended values further below?

  • kernelLatency data counter
  • deviceLatency data counter
  • queueLatency data counter

http://pubs.vmware.com/vsphere-51/index.jsp?topic=%2Fcom.vmware.vsphere.monitoring.doc%2FGUID-308BEF...

The best ways to determine if your vSphere environment is experiencing disk problems is to monitor the disk latency data counters. You can use the advanced performance charts to view these statistics.

    

  The kernelLatency data counter measures the average amount of time, in milliseconds, that the VMkernel spends processing each SCSI command. For best performance, the value should be 0-1 milliseconds. If the value is greater than 4ms, the virtual machines on the host are trying to send more throughput to the storage system than the configuration supports. Check the CPU usage, and increase the queue depth.

    

  The deviceLatency data counter measures the average amount of time, in milliseconds, to complete a SCSI command from the physical device. Depending on your hardware, a number greater than 15ms indicates probable problems with the storage array. Move the active VMDK to a volume with more spindles or add disks to the LUN.

    

  The queueLatency data counter measures the average amount of time taken per SCSI command in the VMkernel queue. This value must always be zero. If not, the workload is too high and the array cannot process the data fast enough.

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joerockt
Contributor
Contributor

Since I was looking for the same thing and found the answer myself, I figured I would post here to help out.

Under Performance, Advanced you will see "Chart Options".  Click that and it will bring up the "Customize Performance Chart", click on Disk, then Real-time and you will see many aditionall options, among which will be Queue write latency, Queue read latency, and Queue command latency. 

HTH

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