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HP LTO-2 Ultrium 400GB Data Cartridge (C7972A) only back ups 280 gb using symantec baCKUP EXEC 10 R3

Created: 01 Jan 2013 • Updated: 01 Jan 2013 | 2 comments
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Hi all,

We have Symantec Backup Exec 2010 R3 to backup our data on a set of HP LTO-2 Ultrium 400GB Data Cartridge (C7972A) tapes, the problem is that the tape only backup 280gb instead of its full capacity 400gb, kindly what I am missing here?


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CraigV's picture


You will never get 2:1 compression, ie. 400GB on a 200GB tape, or any other tape for that matter. The real world isn't the ideal place to get a tape manufacturer's compression ratio.

The ration you're getting is probably spot-on for LTO2. You can try forcing the backup job to use Hardware compression, otherwise Software in the job to see if this gets a bit more. 1.4:1 is what you're getting which is pretty good.

Compression depends on the type of data being backed up. Some data, like photos, zip files etc. don't compress anymore.


EDIT: You should also read pkh's excellent article on compression below which explains in more depth.

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pkh's picture

The native uncompressed capacity of a LTO2 tape is 200GB.  400GB is a marketing thing which assumes that you are able to compress your data 2:1.  280GB represents a 1.4:1 compression ratio which is about what you would normally get in real-life.