Measuring Disk Latency with Windows Performance Monitor (Perfmon)

re: Measuring Disk Latency with Windows Performance Monitor (Perfmon)

Hrvoje Kusulja — Sat, 11 May 2013 19:59:20 GMT

It would be nice if we could limit disk i/o per process and/or per virtual machine like in vmware..

re: Measuring Disk Latency with Windows Performance Monitor (Perfmon)

Andrew Vogel — Sat, 13 Apr 2013 13:28:05 GMT

At what level do filter-leel drivers fit in? Anti-virus software applications tend to introduce those and cause IO latency issues that are difficult to confirm without removing the driver on the assumption it's the problem. Comparing two counters would be a great alternative. I've seen articles using kernrate to compare Safe Mode and Normal Mode execution, but that would require physical or console access to test and couldn't easily be done on a remote VM.

re: Measuring Disk Latency with Windows Performance Monitor (Perfmon)

Scott A. — Sun, 27 Jan 2013 23:36:10 GMT

Good Stuff, Flavio!! Glad you got learnt something in ELS and sharing it out! :)

re: Measuring Disk Latency with Windows Performance Monitor (Perfmon)

kreid — Wed, 16 May 2012 09:35:15 GMT

Excellent, just what I was looking for thank you.

re: Measuring Disk Latency with Windows Performance Monitor (Perfmon)

Flavio Muratore [MSFT] — Wed, 25 Apr 2012 16:03:40 GMT

@Ah_Chao,

The unit is seconds but have millisecond precision.

Counter description:

Avg. Disk sec/Transfer (Avg. Disk sec/Read, Avg. Disk sec/Write)

Displays the average time the disk transfers took to complete, in seconds. Although the scale is seconds, the counter has millisecond precision, meaning a value of 0.004 indicates the average time for disk transfers to complete was 4 milliseconds.

This is the counter in Perfmon used to measure IO latency.

For other counters see: Windows Performance Monitor Disk Counters Explained - blogs.technet.com/.../windows-performance-monitor-disk-counters-explained.aspx

re: Measuring Disk Latency with Windows Performance Monitor (Perfmon)

Ah_Chao — Tue, 17 Apr 2012 08:01:05 GMT

what is the latency unit of the counter listed in this article? ms??

re: Measuring Disk Latency with Windows Performance Monitor (Perfmon)

Flavio Muratore [MSFT] — Tue, 21 Feb 2012 18:11:59 GMT

Hello Guys.

This blog post does apply both to Windows VMs and for the for the Hyper-V host as well.

The special consideration for virtual machines has to do with how VMs calculate time. Because the VMs do not have a hardware real time clock, their time may drift slightly and affect the numbers in the counters. Although this is true, perfmon deals with averages and the results should be useful for a disk performance analysis.

The concept described here will be complemented by a blog I am finishing up on how disk queue works. Stay tuned!

Thank you all for the comments.

Flavio

re: Measuring Disk Latency with Windows Performance Monitor (Perfmon)

SJB — Thu, 16 Feb 2012 23:15:00 GMT

@Chang,

read vpivot.com/.../inaccuracy-of-in-guest-performance-counters

Some counters are fine, but time based ones need to be treated with Suspicion. I was sure there was a document floating around which listed which ones where safe.

re: Measuring Disk Latency with Windows Performance Monitor (Perfmon)

Chang — Thu, 16 Feb 2012 21:56:46 GMT

How does a virtualized machine affect the counters? I fight with my VMWare admins repeatedly about how these Perfmon counters are not viable for Windows VMs...

re: Measuring Disk Latency with Windows Performance Monitor (Perfmon)

Dick Svensson — Mon, 13 Feb 2012 22:03:36 GMT

Nice post!

It was short and well written, haven't seen this simple explanation of these perfmon counters. Would love to see similar short post on other important performance counters. The picture added great value, Great work, txs.