Posted on 2006-05-16
Last Modified: 2012-05-05

Using Windows 2003 NTBACKUP to backup exchange 2003 on a PowerVault 114T DELL. Any idea why compression is not working when I select the option during backup? Using DDS HP 72GB tapes, but they are full after 31GB of data.

Thansk for your help
Question by:BHEIRE
    LVL 23

    Expert Comment


    So you only backup 31 GB and your tapes claim to be full?? I would say throw in a cleaning tape.. Also, not al compressions will work as good a the other one.. If you try to compress a jpg file, you might be able to compress 1%. If you try to compress a .txt file, you will get a 98% rate.... Exchange allready compresses it's database due to the maintenance plan, so you will not win all the much while backupping..

    And also, ntbackup is something Microsoft thought they had to throw in to keep user happy. If you need to have a good backup solution, find yourself a 3rd party tool, something like HP Dataprotector..
    LVL 3

    Expert Comment

    Take a look on Symantec (former Veritas) Backup Exec. It is very powerful backup software.
    LVL 8

    Expert Comment

    Thats a 36gb drive, its 72 is compressed.

    you will never get 72gb.

    You are running out of room because you are backing up 31gb of data, and then te next file is larger then 5gb in size, and because it wont fit on the tape it is waiting for the next tape.

    You need to add a second 36gb tape to that drive or buy a larger drive

    3rd party software gets better compresstion rates, i have even heard that NTbackup wont compress at all.

    Author Comment


    Thanks for all your input - The Powervault 114t has a DAT 72 Digital Data Storage tape drive in it, so surely it should be able to compress the data? The tapes in use are HP DAT 72 (Compressed capacity: 72GB).

    Bilbus could you please explain your comments - Thanks


    Author Comment

    An update -

    This is my log file result  - So have Bytes: 41,692,428,008 be written to the tape. Dell claim it should work, please see comment from DELL below

    Backup Type: Normal

    Backup started on 15/05/2006 at 23:55.
    The requested media failed to mount. The operation was aborted.
    The operation was ended.
    Backup completed on 16/05/2006 at 02:47.
    Directories: 0
    Files: 2
    Bytes: 41,692,428,008
    Time:  2 hours,  51 minutes, and  52 seconds


    The operation did not successfully complete.

    From DELL - With this tape drive you should get about 35gb to 70 gb compressed…see info below..

    Data Compression
    By default, data compression is enabled. With this setting, the external tape drive compresses all data written to tape and decompresses all compressed data read from tape. The degree of compression varies due to the type of data being processed. Data with a high degree of redundancy, such as structured database files or graphics files, are compressed most efficiently, often at a ratio of 2:1 or more. Data with little redundancy, such as executable programs, are compressed the least.

    Any ideas??

    LVL 23

    Expert Comment


    It's like they say, if you have multiple files to be backed up, not all files will have an extremely high compression. If you do an online backup of the Exchange database it will not compress much, this explanes that there cannot be added 70 Gb of data on the drive...
    You will either need to have a better tapedrive (which holds a larger capacity) or try and delete files, burn them to disk or find a way to backup less data..
    LVL 8

    Accepted Solution

    right some files compress better then others

    it is rare to get anywhere near the compressed tape size.

    I buy a tape drive based on it native size, the compressed size is just a extra wiggle room

    Dell has a 80gb native drive for $1100.
    i also saw a dell 200gb native drive for $1300 thats alot of storage. But for $200 i would up to the larger faster drive

    If you are running out of space on 36gb native i would look for nothing less then 80gb native to replace it. More is better.

    the rack drive you have(if i am thinking of the correct model) can support upto two tape drives. So you could have 2x 36gb. I have never used a dual tape rack like that so i would find out more information. But really you best bet is to put that DAT drive on another server, and buy the 200gb tape drive

    Yes exchange wont compress very well

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