get-naperfdata counters refresh interval?

I'm writing a script which clones volumes which are not being written to via cifs.  I get the cifs write counter using the following line:

$cifs_ops = get-naperfdata -name volume -instances <volume name> -counters cifs_write_ops | select -expandproperty counters | select value

I've run into an issue where the counter value is persistent ie. CIFs copy finishes, counter value in terms of cifs ops = 8000+ when the share is no longer mounted and ops should be 0.  Is there any way to force an update of the counter value through the PowerShell toolkit?

Re: get-naperfdata counters refresh interval?

Here's a document that describes the various counter types:

You're using a rate counter, which is a cumulative value, so to get the rate over a time interval you must sample the value twice (c1 & c2) at times t1 & t2, then use rate = (c2-c1)/(t2-t1).  Or just take two successive samples a short time apart and ensure the counter value didn't change.

Or you can try Invoke-NaSysstat, which uses the same perf APIs and may provide a value that works in your case.

Re: get-naperfdata counters refresh interval?

Thanks for the tip Clinton.  I'll try that out.