possible disk perf - how to diagnose?

[TedH256]

So on a 4.1 (will upgrade this spring) cluster, there are 2 systems that are having issues: things like time-outs when trying to post updates to the ERP system, and in another case when trying to add drawing files to a "vault" server.

I've been asked to see if the VM guests involved are having disk performance issues that could be causing this -

What is the best/most efficient way to begin looking into it? Is there anything in vCenter that will show us whether there is high disk latency for a vm, for example, or do I have to do IOmeter or similar on each VM in order to discover this kind of info?

[mcowger]

Look at the performance charts for each VM's virtual disk.  Specific the 'device command latency' value. Anything over 10-15 is a problem.

[TedH256]

I do not see that value in chart options. The closest is "highest disk latency" which shows all 0 - so I doubt it's working?

[TedH256]

so OK I was looking at "disk" not "virtual disk" - not sure what the difference would be from a guest perspective? Anyway ... virtual disk does have "read and write latency" values.

None of the values are above 8 even for peaks - and average between 2-3 for the busiest device. Seems OK, I think?

[mcowger]

If your disks are sub 8ms latencies, you don't have a disk performance issue.