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W2K12 Deduplication [Reading Performance]

    Question

  • Hi,

    I've just installed a new 2012 DC server which is going to hold Veeam Backups.

    So I've created a storage pool around 8TB and created a new volume with deduplication enabled but here comes the issue, my reading speed just dropped for about 85% ( I was around 800MB/s and currently have only 110-140MB/s left... ), what's weird is that my writing speed isn't impacted at all.

    The server is clean (no software installed, nothing on the new volume).

    If anyone knows what happened, it would be great help!

    Best Regards,

    Ludovic


    • Edited by 3magroup Monday, July 29, 2013 2:00 PM
    Monday, July 29, 2013 1:59 PM

All replies

  • If your deduplication really works this means instead of a sequential clustered blocks for your file you'll have a bunch of a different places inside metadata. Making long story short: instead of a SEQUENTIAL read you'll have RANDOM read which obviously is much slower (order of magnitude).

    StarWind iSCSI SAN & NAS

    Monday, July 29, 2013 8:36 PM
  • I could agree with you if there was actually something on the volume and that deduplication already ran.

    In my case, the new volume is empty, I've just tried to copy some iso's to this volume (no troubles writing), and copying them back. Or just used some benchmarks like crystaldiskmark. And my dedupe is scheduled for data older than 2days.

    There must be something I'm missing.

    Monday, July 29, 2013 8:42 PM
  • I could agree with you if there was actually something on the volume and that deduplication already ran.

    In my case, the new volume is empty, I've just tried to copy some iso's to this volume (no troubles writing), and copying them back. Or just used some benchmarks like crystaldiskmark. And my dedupe is scheduled for data older than 2days.

    There must be something I'm missing.

    Try playing with dedupe settings (toggle them on and off), get file info on volume and check for running scrubber process. See here:

    http://technet.microsoft.com/en-us/library/hh848450.aspx

    P.S. And don't use crystalXxx as it shows bogus values. In your case synthetic tests say nothing: they either provide a random I/O pattern or fill everything with the same one. Also make sure you use ones working @ file rather then @ block level.


    StarWind iSCSI SAN & NAS

    Monday, July 29, 2013 11:28 PM
  • It seems that I was a little bit in a hurry that I didn't tested the storage pool.

    Dedupe works fine, when I tried; so I've tried disabling/enabling dedupe but nothing happens.

    It seems I've this issue without dedupe at all, just create a spanned VD on my storage pool and the issue occurs.

    No issue on all 4 Volumes without the storage pool.

    First time I've such a problem when using storage pool with a spanned VD, something is wrong...

    Thanks for help!

    Tuesday, July 30, 2013 7:43 AM
  • It seems that I was a little bit in a hurry that I didn't tested the storage pool.

    Dedupe works fine, when I tried; so I've tried disabling/enabling dedupe but nothing happens.

    It seems I've this issue without dedupe at all, just create a spanned VD on my storage pool and the issue occurs.

    No issue on all 4 Volumes without the storage pool.

    First time I've such a problem when using storage pool with a spanned VD, something is wrong...

    Thanks for help!

    Parity Storage Spaces are known to be quite slow (search these forums for more references as there are tons of them) but simple/mirror/spanning should be fine. Weird :(

    StarWind iSCSI SAN & NAS

    Tuesday, July 30, 2013 7:57 AM
  • Yes, I've come across many subject on poor performance with parity SS, but as you said, I've seen this article:

    http://social.technet.microsoft.com/wiki/contents/articles/15200.storage-spaces-designing-for-performance.aspx

    And indeed speeds shouldn't be affected when using simple/spanning.

    Tuesday, July 30, 2013 8:23 AM
  • Yes, I've come across many subject on poor performance with parity SS, but as you said, I've seen this article:

    http://social.technet.microsoft.com/wiki/contents/articles/15200.storage-spaces-designing-for-performance.aspx

    And indeed speeds shouldn't be affected when using simple/spanning.

    Please let us (me) know if you'd manage to find the source of the issues. Thanks!

    StarWind iSCSI SAN & NAS

    Tuesday, July 30, 2013 12:46 PM