Richard Renshaw
07/16/97 01:14 PM
Is anyone else having performance problems with DLT 7000 tapes.
We have a 2 drive/10 tape jukebox from Overland Data that emulates an
Exabyte 210 8mm library. The drives are recognized as DLT 7000 tapes and
we can backup and restore find, but the performance we get is less than
expected. The DLT 7000 is rated at 5 Meg/sec raw and 8-10 Meg/sec
compress, yet in compressed mode the best we get is 3 Meg/sec. I know we
are not getting the 2:1 compression either, since our 35Gig raw/70Gig
compressed tapes fill up at about 60Gig, but that's not enough to drop the
performance below the raw rating. We are running the drives from a pair of
2100 systems, here are their stats:
system 1 system 2
system 2100A 4/200 2100 4/275
memory 256 Meg 640 Meg
OS Digital UNIX 4.0b Digital UNIX 4.0b
controller KZPAA KZPSA
The DLT 7000 uses a differential SCSI connection, so system 1 runs thorugh
a single-ended to differential converter before attaching to the drive. So
here is what the wiring of the two systems looks like: (connector types in
parantheses)
system 1 KZPAA (SE SCSI-2)--------(SE SCSI-1) converter (Diff
SCSI-1)-----------(Diff SCSI-3) DLT 7000
system 2 KZPSA (Diff
SCSI-3)--------------------------------------------------------------------
--(Diff SCSI-3) DLT 7000
Both drives are the only devices on their particular SCSI chain. I am
basing the transfer timings on system dumps that we run from cron on
weekends so there isn't much else of a system load at the time. The
systems are both database servers, and I shut down the database for the
backups.
Any ideas would be appreciated, and I will summarize if I ever figure this
out....
Thanks in advance,
Rick Renshaw
Received on Wed Jul 16 1997 - 19:36:29 NZST