We are currently trying to diagnose an ongoing issue with a clients backup in Backup Exec. They have an LTO4 Drive that they are backing up to. When they backup it fills the tape (which has a capacity of 800 GB), even though it is only 427 GB of data. It then ejects the tape and asks for more media). If you check the capacity on the tape (which has been fully erased before the backup) it tells you that it is using 800 GB on the tape, even though we have only backed up 427 in the backup job.

We originally thought this was the tape drive but when we do a seperate test backup to an external hard drive it backs up properly.

It is almost like anti compression!

We are using Backup Exec 11d. Anyone any ideas?

  • Your second paragraph makes no sense in context with your first paragraph.
    – joeqwerty
    Aug 26, 2011 at 15:35
  • Re-written it to make more sense - thanks. Aug 26, 2011 at 16:00
  • 6
    One guess: They're writing to an LTO3 tape (LTO4 drives can write to these) and the '800GB' capacity they think the tape has is the usual assumption of 2:1 compression, meaning the tape fills up not much past 400GB when given a more realistic data set. Aug 26, 2011 at 16:04
  • 2
    What color are your backup tapes? If they're Yellow then SmallClanger is correct. If they're Green then you've got strange issues.
    – Chris S
    Aug 26, 2011 at 16:37

2 Answers 2


It turned out it was a hardware fault with the drive!


Have you verified the hardware compatability of your tape drive with BE11? BE11 is a few years and 3 versions old now, so if it's a particularly new tape drive it may not be supported, or you may require the latest Device Driver Installer.

The Hardware Compatability List for BE11 can be found at http://www.symantec.com/business/support/index?page=content&id=TECH46703&key=15047&basecat=COMPATIBILITY_LIST&actp=LIST

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