Disk performance

How do you monitor disk performance on mount point on sql cluster? Perfmon is not doing the job. Any other option that could be useful? Please let me know. Thanks.

asked Jul 11 '11 at 11:39 AM in Default

ebzm
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What is missing from perfmon? What OS version are you running? What version of SQL Server?

Jul 11 '11 at 12:03 PM Shawn_Melton

Taking physical disk counters for reads and writes latency analysis on mount points and there is no data at all.

Jul 11 '11 at 01:51 PM ebzm

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3 answers:

select * from fn_virtualfilestats(-1,-1) might provide some help, down at the database device level... Record the output from that periodically (say, every 10 minutes), do some appropriate calculations, and you have a reasonable view of which DB files are most used.

answered Jul 11 '11 at 01:10 PM

ThomasRushton ♦
29.4k ● 6 ● 9 ● 36

I am wondering about how I should analyze/measure the disk response times from fn_virtualfilestats(-1,-1) number of reads and writes. Any suggestions? For example, using perfmon counters, I will take the response time’s greater than 15 milliseconds as good and disk subsystem is keeping up and there is not that much overhead left. And, if it is more than 25 milliseconds, there is a slow performance.

Jul 11 '11 at 01:49 PM ebzm

The fn_virtualfilestats function returns IOStallReadMS and IOStallWriteMS - you can divide that by the number of reads / writes to determine if there's a problem.

(This assumes you've got regular snapshots of the data, and have done the appropriate calculations to show you only the changes per timeslot.)

fn_virtualfilestats documentation is at http://msdn.microsoft.com/en-us/library/ms187309(v=SQL.100).aspx

Jul 11 '11 at 02:43 PM ThomasRushton ♦

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You should really be using DMVs for this kind of information now. Take a look at sys.dm_io_virtual_file_stats and sys.dm_os_wait_stats. They have great information to help identify and troubleshoot disk issues.

answered Jul 11 '11 at 04:31 PM