Barry,

We don't use DDS2 for production backup, but we have seen wondrous
reductions in backup time to our two 7980XC's using Orbit's product.
When our 996-500 was a 992-400, we changed from using the tape drives'
compression to using Orbit's COMPRESS=3 option.  Our backups are
standalone, so lots of CPU capacity was going idle by using hardware
compression.  Using software compression, our backup went from 8 hours
to 4 hours immediately - same number of reels - and we're not
overloading the CPU.

We're getting ready to implement DLT as our new production backup
medium, and we're seeing the same kinds of results on those drives as
well.  With drive compression enabled and using COMPRESS=2, for
example, a large system backup (~85 Gbytes) will take 4.5 hours to two
cartridges in parallel.  Using COMPRESS=3 and disabling drive
compression, the same backup is accomplished in 3.3 hours - a rate of
24 Gbytes per hour!

If you're using COMPRESS=3, be sure that drive compression is disabled
and that you have the CPU capacity to support the number of processes
feeding each backup device.  Also, I'd recommend talking to Orbit's
Tech Support guys about this to ensure that you're correctly configured
for your system.  They've been a big help to us getting our backups
tuned properly.

Lee Gunter          [log in to unmask]
HMO Oregon


______________________________ Reply Separator _________________________________
Subject: [HP3000-L] BACKUP3000 AND HARDWARE COMPRESSION
Author:  [log in to unmask] at ~INTERNET
Date:    12/27/96 2:20 PM


     Since our 957 does not support hardware compression on the 4mm DDS
     drive I have disabled the hardware compression on the 4mm DDS2 drive
     in our 959.  As an experiment I have enabled the compression on the
     4mm DDS2 drive in our 959 and started a full backup.  We use
     BACKUP3000 from Orbit Software with the COMPRESS=3 option, which is
     the highest compression.  There does not seem to be any significant
     decrease in backup time.  Does anyone else have any experience with
     this?

     Thanks,

     ---------------------------------------------------------------
     Barry Durand             "The opinions expressed in this
     Systems Engineer II       email are not necessarily the
     Gulf South Health Plans        opinions of my employer"
     [log in to unmask]
     ---------------------------------------------------------------