Anything over 400 GB means that compression is being enabled on the tape
drive because you're getting more than the nominal uncompressed capacity
marked on the tape (400GB MAX is what would fit without any compression
enabled). The total amount of data that fits on the tape will vary from
tape to tape because not all data compresses the same... The 800GB value
w/compression enabled is an average, not an absolute value that is set
in stone.  If you want to verify that compression is enabled on the tape
drive, you will need some way to query the drive settings themselves...
This should be documented someplace by the manufacturer of the tape
drive... Try contacting whomever produced the tape drive and ask them
how to query the drive settings....   

When you enable compression on a backup via Networker directives, the
size of your save-sets will get smaller because the data is being
compressed on the client before it is sent back to the server to be
stored on media...  Let's say a partition that was backed up FULL
without compression resulted in a 10 GB save-set.... When you enable
compression via directives, that same save-set will end up being maybe 4
to 6 GB the next time it is saved instead of the original 10... This
does put more load on the client CPU because that is where the
compression is being done... 

> -----Original Message-----
> From: EMC NetWorker discussion 
> [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU] On Behalf Of psoni
> Sent: Tuesday, December 09, 2008 8:40 AM
> To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
> Subject: [Networker] Compress Savesets
> 
> Is it possible that the same make of tapes have different 
> capacity to store data ?
> 
> I am using 400GB/800GB LTO-3 tapes and few cartridges have 
> more than 800 GB on them at present with full status.
> 
> 1040 GB  : full
> 940 GB : full
> 783 GB : full
> 927 GB : full
> 1240 GB : full
> 
> There are no compression directives applied to any of the 
> client resources.
> 
> +-------------------------------------------------------------
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