If any of your clients have compression on, the data is compressed
before sending to the TSM server.
When TSM sends it out to the tape drive, it cannot be compressed again
(or by very little).
This is true of any type of compression, with any type of drive.

If you have a mixture of clients compressing & not compressing, there is
simply no way to calculate your true compression ratio on the drives.

The only way you can calculate is to set up a controlled test, where you
are sure none of the client data is compressed.
But as others have mentioned, the compression ratio is very dependent on
the type of data.

Wanda Prather
"I/O, I/O, It's all about I/O"  -(me)


-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Volker Maibaum
Sent: Monday, November 28, 2005 7:43 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: 3592 Tape Compression


Thanks for the answers!
I already assumed that drive compression was on... But I find it a bit
disappointing that the compression ratio is that poor (only 1,4:1). When
you look at the data sheets for 3592 drives they always talk about 3:1
data compression.

Volker

Am Montag, den 28.11.2005, 07:15 -0500 schrieb Richard Sims:
> augment