Hi Chappies,

After having fiddled with the compression settings over the last few days, here 
are my findings:-

But seriously folks, after testing all of the various options, here are my 
findings:-

NO Compression:-

Setting this option, shaved 25 minutes off of the total backup time for our 
main Oracle database, but bizarrely had NO effect on others, and we used the 
same amount of tapes when doing the storage pool backups.

DRIVE Compression

Using this option, cut 28 minutes off of the total backup time for our main 
Oracle database, 23 minutes off of  another DB, and 29 minutes off of another, 
and we used 1 less tape when doing the storage pool backups (this is arguable 
though, as the number of tapes we use can go up or down 1 or 2, depending on 
drive errors, etc).

Under the original circumstances where CLIENT compression was used, this 
obviously took more time, as it was compressing the data BEFORE sending it to 
the server.

As I said earlier this week though, there IS a negative side to all of this, in 
that the storage pool backups (copies of our main storage pools that get sent 
offsite for DR purposes) now take 4 hours, where typically it used to take 2 
hours. Interestingly enough, migration from DISK storage pool to tape storage 
pool is NOT affected.

So, as you can see, it's a question of what is preferred - quicker COLD backup 
times balanced against crippling storage pool backup times.

One thing you can rely on though - DONT rely on the "Estimated Capacity" figure 
of a tape in TSM - it actually means very little....

Thanks to everyone for their input!!!

Kind Regards,

Roy Lake
TBG European IT
Tel: 0208 526 8883
E-Mail: rlake AT axial-tbg DOT com



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