Hi All,

we normally recommend 'not using TSM Compression' becaus the
fantastic 3592-drives are doing the compression very well and fast.

If users want to encrypt their data with the tsm-client I tend to
recommend also using compression because data would be first get compressed
and then get encrypted (on the client).
This should help save some space on the tapes but it is only an assumption
and possibly compression is not essential.

my question is
If I have a 10GB file and this would appear (without Client-compression and 
without
client-encryption) as 6GB on the tape (after the hardwarecompression) ...

... is it possible to say something about what happens if I set up
TSM Encryption (AES128) and send this file again - now encrypted ?
Wil this data  appear
  more at around 6GB,  more at around 10GB, somewhere between  ?
Or is it something completely unpredictable ?
Statistics would be also interesting

If it is more at 10GB it makes sense using TSM client-compression just to save 
space.
Because of the recently discussed problems with restoring
tsm-compressed data that is aleady compressed by any software
then the comressalway-Option shouldn't also be used there
to avoid problems at restore-process ?

thanks in advance for any hints
Rainer


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Rainer Wolf                          eMail:       rainer.wolf AT uni-ulm DOT de
kiz - Abt. Infrastruktur           Tel/Fax:      ++49 731 50-22482/22471
Universitaet Ulm                     wwweb:        http://kiz.uni-ulm.de