"ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU> wrote on 04/20/2006
01:18:14 PM:
> The way the LTO2 drives seem to be working is that although the
compressions
> settings within TSM are the same, and the servers were just migrated
from
> one server to the other, if the tape were listed 20/40 it is only
storing 20
> instead of 40GB. That is not what the 3590 is doing. I would have
expected
> to see this same data on a tape listed at 200/400GB closer to the 400GB
> compressed value and not the 200GB value.
>
> So I think the question still remains how to reach that upper limit
instead
> of the lower? Is there a TSM setting I have missed? Is there a drive
setting
> that needs adjusting on the drive itself?

You missed the point of what Richard was saying. The amount of compression
a particular tape gets is entirely dependent upon the data you're backing
up. If it's easily compressable (text files, relatively empty database
files, and such), you'll get much closer to 400GB (you may even get more),
while if it's *not* compressable (full database files, binaries, and
such), you'll get closer to 200GB. I have had LTO tapes that fill at 95%
of the uncompressed size, and others that have filled at 125% of the
compressed rating.

There is no TSM setting that will affect the compressability of client
data.

--
Mark Stapleton (mark.stapleton AT usbank DOT com)
US Bank MR Backup and Recovery Management
Office 262.790.3190
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