Tape Compression Blues RRS feed

  • General discussion

  • I am running DPM 2010 with a single HP LTO-5 tape drive.  HP has tested the drive and it is working fine; including the ability to compress data.  The problem is I am only getting 1.4TB of data on a tape.  I have tried turning compression on and off, and the results is the same.  I can't believe that none of my data is compressable.  I understand I may never get to the 3TB level that 2:1 compression would give me, but it does seem that I should get 2 to 2.5TB of storage.

    Has anyone else run into this problem?  Is there a way to tell if compression was turned on for a particular job?  Is there a log?  What have people seen with other tape drives as to compression levels achieved?

    Wednesday, January 26, 2011 9:40 PM

All replies

  • Hi Ron!

    Regarding the comression it could be a tricky part. Different data can be compressed with different ratios. For example, a database could be more  compressed than a flat file, so my point is that it depends of what data your backing up and compressing.

    Now to the other question wheter the compression is enabled or not. If you run through your wizard of the protection group where you have enabled the long-term protection you will come to the window that gives you the option to compress the data written to tape or not. If you have choose to compress data here then the data will be compressed as much as possible.

    A little tip, don't enable hardware compression on your tape drive. I have been in contact with companies that the IT admin has enabled the HW compression of the tape drive and the result is that the tape drive stoped function in DPM since the block size of the written data isn't the same size. Just a little tip.



    Robert Hedblom

    Check out my DPM blog @

    Thursday, January 27, 2011 12:54 PM