Justin
Sorry, I had the same problems with LTO3 and I could not get this to
work. 

Ive moved to LTO4 now, and have to say I am impressed with the
compression we get now and if anything, its faster and better.

But I would be interested to hear from others as well :-)

Simon

-----Original Message-----
From: veritas-bu-bounces AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of Justin
Piszcz
Sent: Wednesday, January 27, 2010 1:41 PM
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: [Veritas-bu] Question with Tape Compression: Is it possible to
turnit off?

Hello,

If you backup highly compressed files, it carries with it anywhere
between 1-5% overhead overall.

Example: 400GB LTO-3 Tape
Example: ~367GB and the tape is FULL:

LTO-3 TAPE:
XXXXXX   9     44   12/10/2009 04:46  12/10/2009 10:13  hcart3
367050755     0
               MPX   INFINITY              N/A         FULL

You can disable compression on a tape drive using the mt command,
however, NetBackup will re-enable it:

>From Symantec:
There is no direct way to turn off hardware compression from NetBackup.
If you use mt command to set the compression, it is effective only for
the currently loaded tape. Once the tape is unloaded the default
compression setting takes into effect. You will have to contact  the
hardware vendor to disable the tape compression

It is also not possible to disable tape compression on the drives via
ACSLS (for those who run ACSLS0 with Sun robots.

And the pre and post backup scripts on the client would not help here. 
Basically, there is no 'easy' way to make this work correctly.

The only thing I could think of is if the client called a pre_backup
script and told the media server, "hey, turn compression off" this might
work BUT it would only work if MPX=1 or there was no multiplexing as
there would be other jobs running to that tape drive.  In addition, if
you do have a lot of tape drives on a media server, ugh, you see my
point.

Any other thoughts on this one?

Justin.

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