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  • Avg. Disk Queue Length

    Hi,

    I have a Windows 2003 server (in an NT domain) which is locking up for periods then returning to normal activity. It has around a hundred users and they experience lockups (significant delays in opening & saving documents) but I am told that it is only NT client users that experience the problem

    I have been running Performance Monitor on the system and it shows very high "Avg. Disk Queue Length" and it appears to happen at the same time as the delays. What's more I have had Task Manager running simultaneously and monitored CPU performance ... there is no corresponding rise in CPU activity.

    It therefore appears to be disk related so can anyone suggest anything that will bring this queue length down?

    Kyu
    J C Rocks (An Aspiring Author's Journey)
    The Abyssal Void War: Stars, Hide Your Fires

  • #2
    Re: Avg. Disk Queue Length

    I've seen such thing before and as it turned out it was an empty battery of the controller.
    Marcel
    Technical Consultant
    Netherlands
    http://www.phetios.com
    http://blog.nessus.nl

    MCITP(EA, SA), MCSA/E 2003:Security, CCNA, SNAF, DCUCI, CCSA/E/E+ (R60), VCP4/5, NCDA, NCIE - SAN, NCIE - BR, EMCPE
    "No matter how secure, there is always the human factor."

    "Enjoy life today, tomorrow may never come."
    "If you're going through hell, keep going. ~Winston Churchill"

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    • #3
      Re: Avg. Disk Queue Length

      When you say "high average disk queue length" exactly how high is it?

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      • #4
        Re: Avg. Disk Queue Length

        Originally posted by Dumber View Post
        I've seen such thing before and as it turned out it was an empty battery of the controller.
        I would have thought that would show on the DELL OpenManage console ... there's nothing there at the moment.

        Thanks anyway

        Kyu
        J C Rocks (An Aspiring Author's Journey)
        The Abyssal Void War: Stars, Hide Your Fires

        Comment


        • #5
          Re: Avg. Disk Queue Length

          I guess you have the latest firmware and drivers for the card(s)?
          cheers
          Andy

          Please read this before you post:


          Quis custodiet ipsos custodes?

          Comment


          • #6
            Re: Avg. Disk Queue Length

            Originally posted by joeqwerty View Post
            When you say "high average disk queue length" exactly how high is it?
            Well looking at PerfMon it has a scale of 0 to 100 (%) and monitoring Pages/sec, Avg. Disk Queue Length & % Processor Time ... the Avg. Disk Queue Length is up at 100 for very significant lengths of time.

            Kyu
            J C Rocks (An Aspiring Author's Journey)
            The Abyssal Void War: Stars, Hide Your Fires

            Comment


            • #7
              Re: Avg. Disk Queue Length

              Originally posted by AndyJG247 View Post
              I guess you have the latest firmware and drivers for the card(s)?
              That's certainly a possibility ... I will check with a colleague.

              Thanks

              Kyu
              J C Rocks (An Aspiring Author's Journey)
              The Abyssal Void War: Stars, Hide Your Fires

              Comment


              • #8
                Re: Avg. Disk Queue Length

                Disk queue length is not a percentage, it is the average number of read and write requests that are in the disk queue during the sample period. It should be 2 or less for each physical spindle in the disk. Example: If you have a RAID5 disk with four drives then the average disk queue length should be 8 or less.

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                • #9
                  Re: Avg. Disk Queue Length

                  Originally posted by joeqwerty View Post
                  Disk queue length is not a percentage, it is the average number of read and write requests that are in the disk queue during the sample period. It should be 2 or less for each physical spindle in the disk. Example: If you have a RAID5 disk with four drives then the average disk queue length should be 8 or less.
                  OK on the scale of 0 to 100 on PerfMon the Avg. Disk Queue Length is up at 100 for very significant lengths of time.

                  Is there some better way I should be measuring this?

                  EDIT: The system BTW has 2 x 72GB mirrored OS drives and 3 x 136GB drives in a raid 5 array. The RAID 5 array is used for storing group data, home data & NT profiles. I think it may be relevant that the RAID 5 drive has maybe 3Gb space left on it but I am assured by colleagues that space remaining is rarely a factor.

                  Kyu
                  Last edited by Kyuuketsuki; 3rd April 2008, 14:26.
                  J C Rocks (An Aspiring Author's Journey)
                  The Abyssal Void War: Stars, Hide Your Fires

                  Comment


                  • #10
                    Re: Avg. Disk Queue Length

                    what server, raid controller, hard drives are you using?
                    are they internal, or on a SCSI/SAS DAS?
                    ________
                    Grape ape pictures
                    Last edited by DYasny; 6th March 2011, 18:22.
                    Real stupidity always beats Artificial Intelligence (c) Terry Pratchett

                    BA (BM), RHCE, MCSE, DCSE, Linux+, Network+

                    Comment


                    • #11
                      Re: Avg. Disk Queue Length

                      Originally posted by DYasny View Post
                      what server, raid controller, hard drives are you using?
                      are they internal, or on a SCSI/SAS DAS?
                      It's a DELL PowerEdge 1800 with 4GB memory, P4HT /2.8GHz CPU's (shows as 4 CPU in Task Manager).

                      The disc subsystem is SCSI, it's a PERC 4/SC Controller:
                      Array A (Boot): 2 x 72GB mirrored (internal)
                      Array B (Data): 3 x 136GB drives RAID 5 (internal)

                      OS is Windows 2003 standard

                      The firmware BTW is out of date but not excessively so.

                      Kyu
                      J C Rocks (An Aspiring Author's Journey)
                      The Abyssal Void War: Stars, Hide Your Fires

                      Comment


                      • #12
                        Re: Avg. Disk Queue Length

                        To be fair even 1 revision can make a difference for firmware, may at least be worth checking the Dell site to see what was changed as they do provide a changelog from memory. This, of course, could easily be a red herring tho.
                        cheers
                        Andy

                        Please read this before you post:


                        Quis custodiet ipsos custodes?

                        Comment


                        • #13
                          Re: Avg. Disk Queue Length

                          Originally posted by AndyJG247 View Post
                          To be fair even 1 revision can make a difference for firmware, may at least be worth checking the Dell site to see what was changed as they do provide a changelog from memory. This, of course, could easily be a red herring tho.
                          Indeed, I just hadn't thought of it. We will address the issue over the next few days ... unfortunately can't be done quickly as it's a high impact server.

                          Kyu
                          J C Rocks (An Aspiring Author's Journey)
                          The Abyssal Void War: Stars, Hide Your Fires

                          Comment


                          • #14
                            Re: Avg. Disk Queue Length

                            use this DVD to update the server:
                            ftp://ftp.us.dell.com/sysman/OM_5.4.0_SUU_A00.ISO

                            also make sure you have caching enabled on the PERC4SC - you can easily do that if you have OpenManage installed - http://ftp.us.dell.com/sysman/OM_5.4.0_ManNode_A00.exe

                            after that is done verify the hard drives' firmware is up to date as well, especially if you use maxtors

                            here are the instructions on how to update HDD firmware:
                            http://support.dell.com/support/down...&fileid=220030
                            ________
                            TOYOTA OPA
                            Last edited by DYasny; 6th March 2011, 18:22.
                            Real stupidity always beats Artificial Intelligence (c) Terry Pratchett

                            BA (BM), RHCE, MCSE, DCSE, Linux+, Network+

                            Comment


                            • #15
                              Re: Avg. Disk Queue Length

                              Originally posted by Kyuuketsuki View Post
                              I would have thought that would show on the DELL OpenManage console ... there's nothing there at the moment.

                              Thanks anyway

                              Kyu

                              Don't know, but I do know you can find it in the eventviewer. Or at least we could
                              The average queue length is way to high on the moment.
                              However I never ever have seen that any software could do that.
                              I strongly would suggest to upgrade you're firmware and check you're diskcontroller.

                              Edit - bad reading.. Missed page 2
                              Last edited by Dumber; 3rd April 2008, 21:08.
                              Marcel
                              Technical Consultant
                              Netherlands
                              http://www.phetios.com
                              http://blog.nessus.nl

                              MCITP(EA, SA), MCSA/E 2003:Security, CCNA, SNAF, DCUCI, CCSA/E/E+ (R60), VCP4/5, NCDA, NCIE - SAN, NCIE - BR, EMCPE
                              "No matter how secure, there is always the human factor."

                              "Enjoy life today, tomorrow may never come."
                              "If you're going through hell, keep going. ~Winston Churchill"

                              Comment

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