Widnows guest OS disk paging counters

[jkgraham]

I understand there are some Windows performance counters that should be untrusted in the virtual environment. Specifically, cpu and memory counters.

I am curious about the pages/sec, pages inputs/sec and pages output/sec counters. My understanding is that these count the memory pages written to and read from disk. It would seem that these counters could be trusted because the VM thinks it is writing to a SCSI drive. Is this the case, can these counters be trusted from a guest OS?

[spex]

All counters can be trusted, they should be interpreted only in the right way....

Ok time itself is a bit problematic.

In your case you are wright - the pages are written to disk as in a physical world -so you should look to keep these counters as low as always.

Kind regards

Spex

[ilatimer]

Just remember that any counter within a vm based on time i.e. pages/sec are potentially skewed due to CPU scheduling aka time drift.

[jkgraham]

This is good to know. The reason I asked is on one box I see a very high count of Pages Input/sec (number of pages read from disk). This is very bursty, trends show a low average but spikes go into the thousands.

The committed bytes counter (virtual memory) is always well below the Available bytes counter (available pages in RAM ) and page file usage remains below 5%. It is puzzling to me. The application is producing a lot of Page faults/sec and these seem to be hard page faults based on the numbers that I am seeing from the performance counters, but no user is complaining about performance.

ESX reports very similar results for Memory. No ballooning has occured and the Active memory is well below memory consumed and granted.

Thanks for the help.

[jkgraham]

This looks like it may be a problem with an application running in an IIS 6.0 Application Pool. Thanks for the help.