From: Matthew Glanville

Joe,

I do not believe there is such a thing as 'server' level compression.  My
understanding is that the device class compression settings are reflectin=
g
the hardware level compression settings, they can override what the
microcode may have set the 'default' to.

We have no problems at all with clients that compress with the tsm client=
,
and then compress again on the tape drive, you loose just a little bit of
space, and yes, the occupancy information does not know that the data has
already been compresssed.  There is really nothing wrong with compressing
data more than once, the files get a bit bigger, but it could be worth th=
e
time and bandwith saved.  Also don't forget that lots of data is stored
already compressed in zipped files or compressed images like jpeg and mpe=
g.

I would not touch with the compression settings on the device class, keep
them on at the highest level, just turn on or off the TSM client
compression as needed.  Check and see if that helps your low bandwith
backups.

Matthew Glanville
matthew.glanville AT kodak DOT com





"Wholey, Joseph (TGA\\MLOL)" <JWholey AT EXCHANGE.ML DOT COM>@VM.MARIST.EDU> on
01/30/2002 01:39:10 PM

Please respond to "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>

Sent by:  "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>


To:   ADSM-L AT VM.MARIST DOT EDU
cc:
Subject:  Re: low bandwitdth and big files


Matt,

Are you running two, maybe 3 compression routines.  i.e.  once at the
client, once at the server level (you'll see if you q devclass f=3Dd on a
sequential storage device) and once at the hardware level
(micro code).

If so, have you kept check on the amount of data in your stgpool.  I say
this because a q occ on a file space is not going to give you an accurrat=
e
indication of the amount of data that node/filespace
has dumped into your stgpool.
Although the IBMers and the manuals say "don't run multiple compression
routines", they've yet to advise on what to do if you have to run client
side compression due to a slow network.  I can shut off
server side/devclass compression, but what about hardware compression.  C=
an
you shut off compression on a 3590 tape device.  Isn't that a micro code
issue.  i.e.  you can't shut it off?

Regards, Joe