How to Enable Compression Back Up on LTO-5 Ultrium Data Cartridge to maximize 3TB of storage

Posted on 2012-08-16
Last Modified: 2012-08-20
Dear Expert,

How can I utilize the 3TB Storage (Assuming 2:1 Compression) of a LT0-5 Tape during back up.
I'm using Symantec Back UP Exec for the Back Up Software agent and HP MSL2024 Autoloader for LTO-5 Tape back up.

When I check the logs on the TAPE Storage Utilization after my first Back Up it only indicates 1.5GB of total size capacity of the tape.

Please help, we are performing our Mid Year Archive.

Thank You,

Question by:kidrock009
    LVL 14

    Assisted Solution

    This support page has screenshots to tell you exactly where to look to use software compression or hardware (faster) compression.
    LVL 55

    Expert Comment

    Bear in mind that "1. The tape drive may be trying to compress data that is already compressed or encrypted. If the data cannot be compressed any further than it already is, the attempt may cause the data to expand." in the above document doesn't apply to LTO since they always pass the compressed and uncompressed data and then pick whatever is smaller to write to tape.
    LVL 20

    Accepted Solution

    There are two numbers you need to know about tape capacity:
    1) Native Capacity: This is how many actual bytes the tape can hold.  In the case of LTO-5, that's 1.5 TB worth of bytes.
    2) The "with compression" number -- usually assumes 2:1 compression.  This is the number that the marketing folks usually get put on the packaging, with a little asterisk.  For LTO-5, it's 3 TB.

    The problem with compression is, maybe your data compresses at 2:1, and maybe it doesn't.  Text documents tend to compress well, about 2:1.  However, a great deal of data is already compressed, and will compress little if at all (examples: jpeg, mpeg, PowerPoint).

    So -- as long as you've selected "use HW compression" you'll be using the compression engine of the tape drive, and will get all the compression you can get by the tape drive itself.

    That said -- there are some compression engines that can achieve somewhat better compression than the LTO hardware -- BUT they are very processor-intensive, and that means that your overall backup performance will be slower (taking as much as twice as long).   The difference in compression is rarely worth the additional steps in backup and restore, given the much slower backup times and complexity of the added process.

    Do NOT use both HW (tape drive) and SW (backup application) compression, as you won't get any additional compression benefit, you'll just slow down the backup job.

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