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[Problem] Delay time on start copying

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  • [Problem] Delay time on start copying

    Hi!
    I am trying to copy huge files from local SAN disks with very high performance. Usually it is fine.
    OS is Windows 2003 R2 32bit.
    SAN File system is Stornext.

    Sometimes, the copy is stuck on 0% for some seconds or minutes without any error or activity and then at some time later the copy starts and goes well.

    I do not know why.

    Do You have some ideas?

    Attach a screenshot.
    Last edited by camillo777; 10-Nov-2011, 12:00 PM.

  • #2
    IOReads and IOWrites are stopped.
    See attached pics.

    Comment


    • #3
      After investigating a bit it seems that it happens when a file needs to be overwritten; not at all when a file is copied from scratch.

      So my temporary solution for now is to delete the right files (to be copied over) and start the copy.

      Do You have any idea why this is happening?

      Thanks!

      Camillo

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      • #4
        Hello,

        Not yet. You mention the local side is a SAN file system, is the destination a remote SAN system? Is it accessed as a Windows Network Share (\\computerName\folder) in the BC3 Folder Compare? From your screenshots, both source and destination are drive letters, but is either or both network locations?

        If you perform the copy as an overwrite, does it hang 100% of the time, even on a test of just one file?

        If you repeat that test using My Computer (Windows Explorer) instead of BC3, does the same behavior occur?
        Aaron P Scooter Software

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        • #5
          Originally posted by Aaron View Post
          Hello,

          Not yet. You mention the local side is a SAN file system, is the destination a remote SAN system? Is it accessed as a Windows Network Share (\\computerName\folder) in the BC3 Folder Compare? From your screenshots, both source and destination are drive letters, but is either or both network locations?

          If you perform the copy as an overwrite, does it hang 100% of the time, even on a test of just one file?

          If you repeat that test using My Computer (Windows Explorer) instead of BC3, does the same behavior occur?
          Yes source and destination are 2 SAN volumes (no network share), FC direct attach storage (via FC switch).
          It seems that also copying by Windows has the same behaviour.
          After thinking a lot of seconds then it starts and the copy is really fast.
          Maybe You have some hints to understand what is happening.
          Network is not used at all.
          Other FS performance are just fine.

          Comment


          • #6
            What brand of SAN are you using? Depending on the provider, the delay may be a function of the architecture -- some storage solutions only copy the changed portion of a file when overwriting an existing item, and the delay you are seeing might be the time spent analyzing the copy to see which portions can be left as is. Since many updates only affect small parts of large files, this is actually a performance enhancement mechanism.

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            • #7
              Originally posted by tlscales View Post
              What brand of SAN are you using? Depending on the provider, the delay may be a function of the architecture -- some storage solutions only copy the changed portion of a file when overwriting an existing item, and the delay you are seeing might be the time spent analyzing the copy to see which portions can be left as is. Since many updates only affect small parts of large files, this is actually a performance enhancement mechanism.
              Storage is DDN 9900
              File system is Stornext 4.1.3

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              • #8
                If it has the same performance in BC3 and Windows Explorer, it is likely an issue with the SAN. I would suggest some tests to try and narrow down what combination of factors cause it. If you switch the Source to a local drive, does that help make it faster? Or if you copy from SAN to a temp local?
                Aaron P Scooter Software

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                • #9
                  Could be fragmentation of target SAN files?

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                  • #10
                    Could be. Did you get a chance to try against a local test drive (that is probably not as fragmented)?
                    Aaron P Scooter Software

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