Tape Drive Compression

[rcflyer0623]

I have a Sony SDT9000 capable of 12/24!! my tapes are 12/24 also. I do not know how to make them get the maximum compression. Anyone have any ideas. I would appreciate it!!

[Keith_Langmead]

The 12/24 GB rating on your tapes, or in fact any x/y rating on different tapes is purely a theoretical maximum, which unfortunately has little or no relation to the real world. Most people find that their backups will get a compression ratio or around 1.1:1 or 1.2:1.

You might get more than that if you're lucky, depending on the type of data you are backing up, for instance large amounts of text, uncompressed graphics etc will get a very high compression ratio, whereas binary data, compressed graphics, movies etc will get very little or no compression.

It's annoying really that the tape manufacturers all seem to use this numbering convention when in fact it bear resemblence to reality.

Personally I never consider the possible compression ratio when considering tape requirements since it's too variable.

Keith

[rcflyer0623]

How do i configure compression on my tape drive. I only am getting 11 gig!!

[Keith_Langmead]

Well hardware compression depends on the tape drive itself, so you'd need to check the hardware documentation for that, but the software compression option is configured within the job setup itself. Safest option really is to choose the option for Hardware compression where available, otherwise Software.

However if you're only managing to fit 11GB onto the tape I'd be concerned about the health of the tapes themselves. Are they fairly new, or have they been in use for a while. Alternatively, it may be that the type of data you're backing up is already very compressed, or of a type that it won't compress any further. In which case the act of trying to compress the data even more can have the effect of actually making the resulting data larger than originally. So it might be worth as a test turning off compression completely and see what happens then.

[rcflyer0623]

They are new, i just do not know much about Backup Exec.

[Rucha_Abhyankar]

Hello Jeff,

Please go through this document:

Compression Ratio does not display or displays incorrectly when using software compression.


http://seer.support.veritas.com/docs/273089.htm


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