Is anyone using magnetic libraries hosted on ZFS?

Last post 07-20-2010, 10:32 AM by Dannie. 5 replies.
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  • Is anyone using magnetic libraries hosted on ZFS?
    Posted: 07-13-2010, 9:54 PM

    Curious to see what performance is like with Simpana v8 and a magnetic library on top of ZFS, with Compression/Dedupe on and off..


    Cheers,
    Luke
    (@cv_skywalker)
  • Re: Is anyone using magnetic libraries hosted on ZFS?
    Posted: 07-15-2010, 12:45 PM

    Hello Sky,   We do not have many customers trying it on scale.   In my research we had a customer using Red Hat GFS which is similar and had good performance results (no dedupe involved).   We suspect that ZFS and dedupe would not necessarily yield benefit because we insert a lot of unique metadata in the backup stream.  Any dedupe solution will struggle with external compression because of block alignment issues.  So we don't see any particular extra benefit to go with this solution over another.

    If you are going with this solution I would recommend you run some tests of your own as each enviroment is very different.


    Mark Spencer
    CommVault, Business Critical Support
  • Re: Is anyone using magnetic libraries hosted on ZFS?
    Posted: 07-19-2010, 7:40 AM

    mspencer:

    We suspect that ZFS and dedupe would not necessarily yield benefit because we insert a lot of unique metadata in the backup stream.

    OK, don't want to hijack this thread, but this surprises me.

    Is this only true for magnetic libraries? We have a DataDomain VTL which ddups everything coming onto the library. Can we tweak Commvault to increase ddup then?


    If it jams, force it.
    If it breaks, it needed replacing anyway.
  • Re: Is anyone using magnetic libraries hosted on ZFS?
    Posted: 07-19-2010, 12:16 PM

    Thanks Dannie-  I just mean that using ZFS would not really give extra benefit.  

    Are you asking if you can increase dedupe for you data by using our dedupe on top of the dedupe solution you already have in place with the Data Domain? 


    Mark Spencer
    CommVault, Business Critical Support
  • Re: Is anyone using magnetic libraries hosted on ZFS?
    Posted: 07-19-2010, 12:25 PM

    DataDomain takes special exceptions for data coming from CommVault to work around these issues.  When you configure the DataDomain system, you tell it what kind of tape marker it should expect and it treats that data differently then normal backup data. 

    In addition, DataDomain is using Variable Length Segments to chunk up the data into bits that it can deduplicate.  Overall, Variable Length Segment Deduplication systems get better deduplication rates than Fixed Length Segment systems.  I don't know how ZFS does its deduplication, but it would be worth looking into.

  • Re: Is anyone using magnetic libraries hosted on ZFS?
    Posted: 07-20-2010, 10:32 AM

    JasonM:

    I don't know how ZFS does its deduplication, but it would be worth looking into.

    ZFS uses fixed blocks of 256k, inline.
    http://blogs.sun.com/bonwick/entry/zfs_dedup

    Thanks for the explanation about that. I totally forgat we configured the DD for Commvault tape markers :)


    If it jams, force it.
    If it breaks, it needed replacing anyway.
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