Change de-dupe block level size

Last post 05-25-2011, 10:37 AM by Bill Oyler. 2 replies.
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  • Change de-dupe block level size
    Posted: 05-09-2011, 11:46 AM

    We have been running our email and file archvies using 128K blocks. However reading the forums, we believe that 32K will give us better compression. 

    Is is possible to simply change the block size on the storage policy properties?

    Will this only affect new archived items? Or will it affect items already archived?

    Would it make more sense to Aux copy the whole archive using the new block size?

  • Re: Change de-dupe block level size
    Posted: 05-09-2011, 12:14 PM

    You should be able to just change it but it will affect new archived items. 

    When aux copying the whole archive to the new block size, there may be an issue with reading the data with the previous block size when aux copying it off.  You may want to set up a new secondary copy and run a test aux copy to it to see if it causes any technical issues.


  • Re: Change de-dupe block level size
    Posted: 05-25-2011, 10:37 AM

    Assuming you are on v9, you may want to keep your block size at 128 KB.  I just received an updated best practices guide for dedupe from CommVault and it states that 128 KB is the "new recommended" block size for dedupe:


    "Dedupe Block Size: 128K; New Recommendation based on increased capacity of DDB Engine and last block fix"


    I confirmed with our local CV SE that 128 KB should be used for all types of backups (file system, e-mail, VMware, databases).  This seems surprising to me but unless I hear otherwise I will take this into consideration going forward.

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