SQL Server Performance

Enabling Diskperf -ye for PerfMon's logical disk counters

Discussion in 'SQL Server 2005 General DBA Questions' started by jbates99, Aug 20, 2010.

  1. jbates99 Member

    hi everyone,
    I'm running 2005 on a Windows 2003 server and I suspect I have a bottleneck in disk I/O.
    I have read that if I run Diskperf -ye (at the command line) then reboot the server..... I can then use the logical disk counters in Performance Monitor.
    A couple of questions.
    How can I determine if diskperf -ye is already enabled? In PerfMon, I do see the counters for Logical Disk - does this mean I can use them and get accurate results?

    Anyone had experience with enabling the use of logical disk counters?

    Thanks, John
  2. Luis Martin Moderator

    How can I determine if diskperf -ye is already enabled? In PerfMon, I do see the counters for Logical Disk - does this mean I can use them and get accurate results?
    Yes.
    What about Average Disk Queue Length?
    Did you run Profiler?. Found long queries with high reads?.
    What issue do you have to blame disks?

  3. jbates99 Member

    Thanks, Louis.
    Avg Disk Queue Lenght is high - at a value of 71. But thats for Physical Disk
    We have SANS and are using Pillar storage.

    I know if you have local physical drives you divide the 71 by the number of drives to get an accurate value for Avg Disk Queue Lenght.
    When I ask the system engineers how many physical drives..... well I get various answers. I think our advanced storage may require that I use a different tool for tracking Disk IO and perfomance .
    We are now experimenting with a tool that's part of the Pillar software. That may give us a better idea. I will post back later.
    John
  4. satya Moderator

    As Luis referred and since Windows 2003 server edition those logical counters are enabled by default, you can also get information from diskperf /help to see "Disk performance counters are permanently enabled on systems beyond Windows 2000".
    Also look at REGISTRY - HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesPerfDiskPerformance - locate the Disable Performance Counters value in the details pane. If the data value is 0, the counters are enabled and if the value is 1, the counters are disabled.
    The other point you referred that SAN using third party storage. See this http://www.sql-server-performance.com/tips/monitor_io_counters_p1.aspx on this site on monitoring the important IO counters, so if you get performance issues then
    reason is that many SQL Server instances use storage on a SAN that's improperly configured for their workload and that shares resources with other I/O-intensive applicaitons. Also see thsi http://www.eraofdata.com/blog/2010/02/misaligned-disk-partition-offsets-and-sql-server-performance/ blog post for further reference.

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