multiple tablespaces containers on SAN

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  • paul
    #1

    multiple tablespaces containers on SAN

    Hi,
    i want to know if this is better to split a tablespace into several
    containers while the database are on san disk.
    And how can i configure optimally the values for prefetch and extend ?

    thx


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    • Lew
      #2
      Re: multiple tablespaces containers on SAN

      I would say the answer is almost always yes. How you set it up exactly
      depends on the way your logical disk volumes and file systems are
      mapped to the backend storage packs. The values for prefetch and
      extentsize are somewhat (but not entirely) related to how the data will
      be accessed.

      Lew

      paul wrote:
      Hi,
      i want to know if this is better to split a tablespace into several
      containers while the database are on san disk.
      And how can i configure optimally the values for prefetch and extend ?
      >
      thx

        Comment

        • Ian
          #3
          Re: multiple tablespaces containers on SAN

          paul wrote:
          Hi,
          i want to know if this is better to split a tablespace into several
          containers while the database are on san disk.
          Assuming you have DB2_PARALLEL_IO set properly (to enable DB2 to issue
          multiple I/O requests to each container) then the answer is no.
          Spreading your tablespace across multiple containers in the same
          file system will result in I/O contention at the disk level.

          Use 1 container per RAID array in the SAN device (note, multiple LUNs
          may exist on a single RAID array, so make sure you understand the
          mapping from file system -LUN -RAID array).
          And how can i configure optimally the values for prefetch and extend ?
          Extent size should be set to the strip size (or a multiple thereof) of
          the RAID arrays in your SAN device. Prefetch should be set to ensure
          that all disks are serving data for a prefetch request.

            Comment

            • paul
              #4
              Re: multiple tablespaces containers on SAN

              hi
              thanks for your comment, i'll check this with the san administrator

              paul

              "Ian" <ianbjor@mobile audio.comwrote in message
              news:zGr0h.842$ m17.289@newsfe0 8.phx...
              paul wrote:
              Hi,
              i want to know if this is better to split a tablespace into several
              containers while the database are on san disk.
              >
              Assuming you have DB2_PARALLEL_IO set properly (to enable DB2 to issue
              multiple I/O requests to each container) then the answer is no.
              Spreading your tablespace across multiple containers in the same
              file system will result in I/O contention at the disk level.
              >
              Use 1 container per RAID array in the SAN device (note, multiple LUNs
              may exist on a single RAID array, so make sure you understand the
              mapping from file system -LUN -RAID array).
              >
              And how can i configure optimally the values for prefetch and extend ?
              >
              Extent size should be set to the strip size (or a multiple thereof) of
              the RAID arrays in your SAN device. Prefetch should be set to ensure
              that all disks are serving data for a prefetch request.
              >

                Comment

                • mike
                  #5
                  Re: multiple tablespaces containers on SAN



                  Use 1 container per RAID array in the SAN device (note, multiple LUNs
                  may exist on a single RAID array, so make sure you understand the
                  mapping from file system -LUN -RAID array).
                  >
                  The DB2 publications continue to advise to use one container per
                  tablespace when using RAID devices.

                  Is that always the best advice ?

                    Comment

                    • Mark A
                      #6
                      Re: multiple tablespaces containers on SAN

                      "mike" <_link98@yahoo. comwrote in message
                      news:1162280190 .398259.17370@m 73g2000cwd.goog legroups.com...
                      >Use 1 container per RAID array in the SAN device (note, multiple LUNs
                      >may exist on a single RAID array, so make sure you understand the
                      >mapping from file system -LUN -RAID array).
                      >>
                      >
                      The DB2 publications continue to advise to use one container per
                      tablespace when using RAID devices.
                      >
                      Is that always the best advice ?

                      Probably is the correct advise for most systems, depending on the throughout
                      of you RAID controller.

                      However, unless you have a data warehouse and are doing a lot of table
                      scans, it doesn't matter much, one way or the other. Check your buffer pool
                      hit ratio, and if it is above 95%, don't even worry about it.


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