It all boils down to where your bottle neck is...
If your client(s) have hugh amounts of data and big enough engines to
compress it down and it compresses nicely (such as oracle DB's) then you
will find that you can compress the data AND send it in less time than you
can send the data uncompressed.
Or if you don't have much network band width and your users go across the
same network as your backups then you might want to compress the data to
minimize the traffic.
Example... we have an SAP instance that is about 2.4 TB on an E10000 with a
dozen (or more) processors and an independent network for backups... with
compression turned on we can now back this DB up in about 16 hours which
basically keeps the 100 Mb/sec fast ethernet interface maxed out... and
because we can keep it maxed out, if we sent the data uncompressed it would
take 4 times as long because it would be sending 4 times the bytes (we see a
pretty good 4/1 compression)
So I get to say my favorite thing
It depends !
later,
Dwight
-----Original Message-----
From: Roy Lake [mailto:[EMAIL PROTECTED]]
Sent: Thursday, March 08, 2001 5:30 AM
To: [EMAIL PROTECTED]
Subject: Compression / No Compression ???
Hi Chaps,
Just wanted to share my findings with you with regards to TSM compression/no
compression.
We have 3575-L18 tape library. We use 3570-C Format tapes. We used to have
CLIENT compression set to YES when doing backups, with DRIVE compression
OFF. Most of the data on our systems is Oracle. When we had client
compression set to YES, each cartridge would take about 5GB.
I have done some testing and found that when I switched compression OFF, we
managed to get around 21GB on each cart, and also the backups were a LOT
quicker.
IBM recommend (and I quote:) "Oracle databases are normally full of white
space, so compression is required. Either h/w or client compression."
Could someone please explain WHY compression is required if we get more on
tape with it switched OFF, and the backups are quicker?.
In our environment, TSM has its own 10Meg a sec network, and 99.9% of the
backups are done overnight, so there is no problem with performance issues.
Am I missing something here, or is it REALLY a better idea to forget about
compression totally?.
Kind Regards,
Roy Lake
TBG European IT
Tel: 0208 526 8883
E-Mail: [EMAIL PROTECTED]
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