Huge Aux Copy Performance Boost with Multiple Copies

Last post 04-18-2017, 2:11 PM by AndyHengst. 3 replies.
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  • Huge Aux Copy Performance Boost with Multiple Copies
    Posted: 03-18-2012, 8:40 AM

    I think I've just discovered something by chance that has completely floored me.

    I have a bunch of policies with a primary dedupe disk copy and a pair of secondary copies going to tape.

    I've always started an Aux Copy with the defaults i.e. all copies, maximum streams, which meant that for each policy running an Aux Copy fired up a single auxcopy.exe process on the MA with two streams, one to each tape.

    Performance was all over the shop, very unpredictable and quite low - nowhere near the throughput that the disk or both drives can support.

    It seemed obvious something wasn't right as doing a data verification job on the source job using the same streams was giving phenomenal throughput.

    So, I just tried something which was to start two aux copy jobs for the policies, one for each secondary copy.

    The result is two auxopy.exe process running, and my tape drives look to be running at full speed.

    To say I'm staggered at the difference in performance is an understatement - it's not something I've read about before and I'm assuming it's related to how Commvault managed resources per process.

    Hopefully someone will find this little tip useful.

    Paul

  • Re: Huge Aux Copy Performance Boost with Multiple Copies
    Posted: 03-19-2012, 9:09 AM

    Paul,

    What are the system specs and OS?

     

  • Re: Huge Aux Copy Performance Boost with Multiple Copies
    Posted: 03-19-2012, 9:17 AM

    2008 R2 on a Dell R710 with 2x E5645's and 32gb of RAM with a TL4000 slung off a SAS HBA and a pair of MD1200's chained off a Perc H800.

    4 x 5+1 RAID5 sets (2tb NL SAS) split into 16 x 2tb mount paths.

    Doing a data verification on my last Synthetic Full (so single stream with data scattered all over the spindles the thing screams) - the source disk is not the issue.

    Even with the lookahead reader enabled I seem to struggle to get consistently good throughput to tape on aux copies using 256kb block and 16gb chunk size.

  • Re: Huge Aux Copy Performance Boost with Multiple Copies
    Posted: 04-18-2017, 2:11 PM

    <...a couple years go by...>

    Hi Paul,

    I wonder if the HBA was unable to keep up with multiple tape drives.  Having 4 shoeshining drives might actually be slower overall than 2 satisfied drives.  Not to mention it could jeopardize your recoveries (if tape errors happen to increase).

    How is Dell (drives) for reporting shoeshining? Or are they IBM drives perhaps? I know ours (IBM library) don't actually flag that condition, you either watch the blinkenlights or notice the poor performance.

    Andy

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