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Dedup issue on only one DB?

Discussion in 'Microsoft SQL Server' started by david_stabler, Jan 3, 2012.

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  1. david_stabler

    david_stabler New Member

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    I have a single database, and not one you might think, that won't client-side dedup like it should. After a full happens, I send another, and the full transmission happens again. I'll freely admit the DB is on the large side, but could that be the factor? All the other databases on this SQL server are deduping just fine!

    This log is from the most recent full backup that was attempted.

    Type: SQL Server
    Action: Legacy Backup
    Components: [redacted DB name, 28 characters long]
    Status: Successful

    Total SQL backups selected: 1
    Total SQL backups attempted: 1
    Total SQL backups completed: 1
    Total SQL backups excluded: 0
    Total SQL backups inactivated: 0
    Total SQL backups deduplicated: 1

    Throughput rate: 25,891.50 Kb/Sec
    Total bytes inspected: 664,055,230,336
    Total bytes transferred: 664,055,230,336
    Total LanFree bytes transferred: 0
    Total bytes before deduplication: 23,936
    Total bytes after deduplication: 23,936
    Data compressed by: 0%
    Deduplication reduction: 0.00%
    Total data reduction ratio: 0.00%
    Elapsed processing time: 25,046.49 Secs

    Any guesses?
     
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  3. rowl

    rowl Member

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    There is a setting CLIENTDEDUPTXNLIMIT which I read defaults to 50GB. I suspect you are running up against that.

    The CLIENTDEDUPTXNLIMIT option specifies the maximum size of a transaction when client-side deduplicated data is backed up or archived.

    You may be able to work around this by backing up the DB with multiple streams so that each stream sends less than the maximum.

    -Rowl
     
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  4. david_stabler

    david_stabler New Member

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    I used SETOPT to update the option file (didn't work), then just restarted TSM. After I did, the next backup came in just fine with a very nice dedup rate (strangely, after doing a few fulls in a row, I got this result:

    Total bytes before deduplication: 658,224,118,656
    Total bytes after deduplication: 28,760,376,005
    Data compressed by: 0%
    Deduplication reduction: 95.64%
    Total data reduction ratio: 95.64%
    Elapsed processing time: 16,363.29 Secs

    Much Better! Thanks!

    )
     
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