Deduplication block size and Application read size

Last post 04-15-2020, 8:32 PM by Saurabh Srivastava. 2 replies.
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  • Deduplication block size and Application read size
    Posted: 04-01-2020, 4:50 PM

    Hi all,

    I have certain doubts regarding application read size and Deduplication block size.

    How are these two - Deduplication bock size and Application read size - connected?


    Suppose if I have set an application read size of 512 KB at subclient level and deduplication bock size of 128 KB at primary storage policy copy.

    My understanding is-  the data will be read from the client server, which is compressed to deduplication buffer of 128 KB and then Signature is generated.  Now, where is 512 KB of Application read size comes into picture?


    A text in the below link is further confusing me-


    Application Read Buffer Size

    For default and user-defined subclients that are newly created from the CommCell Console, Command Center, or command line, the application read buffer size is now 512 KB.

    Previously, the application read buffer size was 64 KB.

    Note that from Service Pack 11 onwards, new baselines for deduplication signature will be created for all newly created subclients because of this change.


    I am not getting how come changing the the application read size will require new baseline for deduplication signature, After all we are not changing the Deduplication block size? right?




    Saurabh Srivastava
  • Re: Deduplication block size and Application read size
    Posted: 04-02-2020, 9:46 PM

    Hi Saurabh,

    we are not changing the block size but the tag header/data changes when the applciation read size changes which changes the hash signature.

    if this has signature does match the existing has signature in the DDB then its treated as new.

    Gary Seibak
    Technical Account Manager - Commvault
  • Re: Deduplication block size and Application read size
    Posted: 04-15-2020, 8:32 PM

    Thanks Gary.



    Saurabh Srivastava
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