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  1. #1
    Super Moderator BATcher's Avatar
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    Backup to external USB hard drive from WS2008R2 takes different times

    At roughly weekly intervals, I plug in a (nominal) 2 TB external USB hard drive into our Windows Server 2008 R2 HP box (which has USB 2.0 sockets only) and back up a number of its partitions using the WBadmin built-in Backup program.

    Although roughly the same resultant amount of data (~70 GB) is backed up each time, the backup times taken cluster around 40 minutes and around 160 minutes, for no obvious reason.

    Can anyone suggest why that might be? I always use the same USB socket to connect the hard drive, and the server is nearly idle on all backup occasions. (Even better would be a guaranteed way to make the backup last 40 minutes!)
    BATcher

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  2. #2
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    The backup software should create a snapshot, then copy that data to the external disk.
    Check the Event Viewer for snapshot information and times.
    Is the server disk / backup disk fragmented?
    What is the USB throughput normally? Use Robocopy to test several copies at different times.

    cheers, Paul

  3. #3
    WS Lounge VIP mrjimphelps's Avatar
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    To make sure that the snapshot is done as Paul described in #2, be sure to include the -vssFull or -vssCopy parameter with your backup command. (VSS = Volume Shadow copy Service.)

    Here is helpful information about WBAdmin.

  4. #4
    Super Moderator BATcher's Avatar
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    It won't surprise you that I am running this backup via a BATch file slightly more extensive than:
    Code:
    :: build up the parameters for wbadmin start backup
    set parms=-backupTarget:%dl% -include:C:,F:,I:,J:,K:,P:,R:,U: 
    set parms=%parms% -allCritical -systemState -vssCopy
    wbadmin start backup %parms%
    Any other parameters will default to the same values each time, I would presume.

    While I appreciate the points you both make, I cannot see why there should be a factor of 4 difference in the time taken from one backup occasion to another. Of course the source and target hard drives are fragmented (have you ever tried to defragment a 2 TB USB external hard drive on a USB 2.0 interface, when it is full of 60-or-so GB files?!), but there will be only a minor difference each time.

    I am postulating that for some reason the USB 2.0 data transfer rate can have two values: High and Low - but how no idea why this could be!
    BATcher

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  5. #5
    WS Lounge VIP mrjimphelps's Avatar
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    If fragmentation were the cause of the backup slowdown, you would see it every time, not every other time.

    On the other hand, if you're doing an incremental backup every time, then there could be a big difference in backup times; but in order for this to happen, there would have had to have been a lot of change to the contents of the drive between backups.

    To shorten the time required for an incremental backup, first do a full backup, then do an incremental backup.

  6. #6
    Super Moderator BATcher's Avatar
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    I always do full backups on this server - and I don't think WBadmin allows incrementals!
    BATcher

    Talking to laser printers can be very effective.
    You just need the right toner voice...

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