Thanks for the reply Allen.  The Sterling backup software is capable of doing 
compression, but we
rely on the hardware compression built into the tape drive (IDRC) which should 
yield around 3:1.
The block sizes written by ADSM and the Sterling product are both 32760 and we 
are also able to
get a full 3390-3 onto a cartridge.  ADSM however is another story.

I have been advised by an IBM/ADSM person to contact their tech support, since 
ADSM should
be getting over 2 gig per cartridge.

Thanks again!
______________________________ Reply Separator _________________________________

3490e carts hold 720 meg non compressed.  If hardware compression yeilds 2:1
then getting 1.3-1.4 gig per tapes is doing well.  As far as your Sterling
backup software is concerned, does it do it's own compression?  What blksize
does it use?  We use FDR, and not only does it do compression, it also writes
larger than 32K block sizes (not readable by anything but FDR) such that *most*
of our 3390-3 (2.7 Gig) backups will fit on 1 cart.

ADSM writes 32760 or smaller blocksizes (at least in AIX).  Smaller blksizes
mean more IRGs and less data per cart.

I run with compression turned on for most clients, and I'm seeing a range of
820-905 MEG per cart with the average somewhere around 850 each. :)

-Al
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