We're currently using DLT4000 equivalents to perform production backups
on both our HP3000 systems.  We also use Orbit's backup software in
conjunction with the DLT's, and we find the performance satisfactory.
Our 996-500 supports three (3) DLT drives - one per SE-SCSI channel -
and experiences throughput of around 30+ GB per hour to all three
drives in parallel and stores about 90 Gbytes to three (3) cartridges.
Our 980-200 gets somewhat less (10-15) for two drives in parallel.

We prefer to use software compression (BACKUP/3000's ';COMPRESS=2'
option) because our backups are run standalone.  We've discovered that
using maximum compression (;COMPRESS=3) has created problems on large
restores where excessive I/O retries/timeouts on slow disk drives can
cause a system failure due to a MIB table overflow.  We do leave drive
compression enabled, although I do want to test backup performance with
this disabled eventually.

We've also experienced problems completing an entire system restore
where BACKUP/3000 can't resolve completeness of a few files at the
conclusion of the restore.  The files are subsequently purged by the
program, and we must try several times to get the last few files
loaded.  Typically, these are large TurboImage datasets.  Orbit is
looking into this, so I don't know what causes this at this time.

Our DLT's are configured as HPC1520B DDS device types, but I've just
changed the 980's drives to HPC1521B to test software compression
control via the DEVTOOL utility (DEVCTRL.MPEXL.TELESUP command file).
I understand that HP's DLT-whatever device type in release 5.5 doesn't
support some features, such as fast search, so we're not using that
configuration.

Lee Gunter          [log in to unmask]
Regence HMO Oregon


______________________________ Reply Separator _________________________________
Subject: [HP3000-L] Selecting the right DLT-drive?
Author:  itdept <[log in to unmask]> at ~INTERNET
Date:    4/29/97 6:32 PM


We plan to move from DDS to DLT. On HP's web you can read a lot about the
new DLT 30e and DLT 40e.
I just talked to our CE at HP - and he says that these DLT stations are not
supported on HP 3000 (but apparently with almost anything else than HP
3000!). Only the DLT4000 is supported, currently.

1) Does anybody know whether this is true or not?

2) It is possible, that the DLTs will run unsupported under MPE anyway?

3) We will be using BACKUP/3000 with the DLT-station - any experiences with
that constellation, anybody?
(I'm thinking on how much you can expect to hold on one tape - using both
the built-in hardware compression
plus ORBiTs software ditto).

TIA!

Hans-Ole Kaae
Manager, IT
Greenlandair Inc.
Nuuk, Greenland

[log in to unmask]
http://www.greenland-guide.dk/gla/