Inline Tape Copy slows down tape driver performance - Veritas Net Backup

This is a discussion on Inline Tape Copy slows down tape driver performance - Veritas Net Backup ; Dear all, I'm experiencing that when I tried to backup my database (which is about 500GB) into 4 units of SDLT 320 tape drive using "Inline Tape Copy" technology (i.e. 2 drive for each sets of backup image), I'm only ...

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Thread: Inline Tape Copy slows down tape driver performance

  1. Inline Tape Copy slows down tape driver performance


    Dear all,

    I'm experiencing that when I tried to backup my database (which is about
    500GB) into 4 units of SDLT 320 tape drive using "Inline Tape Copy" technology
    (i.e. 2 drive for each sets of backup image), I'm only getting about 7.5MB/s
    of throughput. This is about half the throughput we usually get when we
    backup without creating duplicate images using Inline Tape Copy, which is
    about 12MB/s. What might be the reasons? Anyone else experience this issue?
    Hope to hear some suggestions and comments from all the gurus out there!

    Merry Christmas!!

  2. Re: Inline Tape Copy slows down tape driver performance


    I've experienced similiar degradation by using inline tape copy. I noticed
    about a 25% increase in the active backup window. I believe it is due to
    the fact that NetBackup fills a memory buffer with the data being backed
    up and waits until all copies receive the data before clearing the buffer
    and starting the next transaction. The backup runs at th erate of the slowes
    copy. This can delay the backup because an image may fill up a tape in one
    of the copies and will take time to mount and position on the next span of
    tape. The other copies have to wait until that is done before they can continue.
    Perhaps if you use virgin tapes for all copies the inline backup would then
    be about the same as a regular backup. I happily accept the 25% overhead
    for inline copy when I compare it to the alternative of duplication. The
    duplication process would take at least double the time because the image
    would have to be read from an already existing image and write it to tape.

    The greatest benefit I have seen is the restoration of Oracle databases.
    The threads are now able to be restored in a parallel process with the advent
    of inline copy as oppposed to a serial process that was due to the duplication
    process.
    Restore time went from 10 hours to 1 1/2 hours.


    "Adrian" wrote:
    >
    >Dear all,
    >
    >I'm experiencing that when I tried to backup my database (which is about
    >500GB) into 4 units of SDLT 320 tape drive using "Inline Tape Copy" technology
    >(i.e. 2 drive for each sets of backup image), I'm only getting about 7.5MB/s
    >of throughput. This is about half the throughput we usually get when we
    >backup without creating duplicate images using Inline Tape Copy, which is
    >about 12MB/s. What might be the reasons? Anyone else experience this issue?
    >Hope to hear some suggestions and comments from all the gurus out there!
    >
    >Merry Christmas!!



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