Data Compression limit on Backup Tape

[Hazzer]

We use Backup Exec 10d Service Pack 4  and a Quantum Ultrium 2 LTO Backup Drive and compatible 200/400GB Ultrium 2   tapes and have hardware data compression enabled. We have successfully backed up 260GB on one tape overnight, however, more often than not, a further tape is requested to complete the backup usually around 220 -240GB, (this obvoiusly will have some disruption to the network use during the day).

When tapes advertise compression up to 400GB I am a little perplexed as to why I cannot alway complete the backup of 260GB, the files being backup up do not vary a great deal. 

Thanks for any guidance on this topic

Hazzer

[Hazzer]

Any guidance on this matter would be helpful.

[CraigV]

Hi,

You can sometimes get this error if the tapes are old (LTO2s are renowned for worse failure rate than newer LTO technology), or if you're backing up already-compressed data. In this case, there are times where this data is inflated in size ensuring you can't fit your data onto 1 tape.

Check your tapes themselves and see what sort of compression you're getting. 1.4-1.6:1 is normally a good compression ratio.

Also make sure you're using the Symantec drivers for the tape drive.

Thanks!

[PraveenShetty]

Please check the link below :-

http://www.symantec.com/docs/TECH6076

Please mark it a solution, if this is useful.
Thanks

[Hazzer]

Hi

Thanks for your response.

We have recently purchased new tapes as we were advised that the age of tapes may be the reason behind the request for further tapes.

The Tape drive is a Certance Ultrium 2 the driver is supplied by Certance - would this make a different if not a Symantec driver?

I have contacted the tape manufacturers for further information on compression.

Many thanks

[CraigV · Accepted solution]

...there should be a Quantum utility (otherwise check and see if it lists itself as an HP!) that might be able to do a compression test on those new tapes.

If it lists itself as an HP, get hold of HP Library and Tape Tools and put a new tape in that you no longer need. Run the compression test and it will show you what sort of compression you should be getting.

[Hazzer]

Many thanks to all  for useful info suplied.