We had lotsa problems with DDS2 drives.  Most of the problems went away when
we put each drive on a separate card.

                -----Original Message-----
                From:   Jeff Woods [mailto:[log in to unmask]]
                Sent:   Friday, December 11, 1998 12:08 AM
                To:     [log in to unmask]
                Subject:        Re: DDS-3 Troubles

                At 10:26 AM 12/10/98 -0500, Russ Kahler wrote:
                >In the last few months, we have had continued problems with
our DDS-3 tape
                drives. On both of our HP 3000's ( a 967 and 928) we have
experienced a
                serious, sudden drop in throughput on our nightly backups-
from about 1400
                kb/s to around 1100 kb/s (causing the backup to take up to 1
1/2 hours
                longer). This has happened three times to each of our three
DDS-3 drives in
                the last 4 months- with no obvious hardware or software
errors ( the Scsi
                card and cables are good, there is no increase in amount of
data stored,
                and all system resources check out during the backup). It
just seems to hum
                along fine for a few months, and then all of a sudden, the
next morning my
                backup is taking an hour longer than it did the day before.
                >
                >Has anyone out there had any experience with problems such
as these? I
                know tape drives wear out ...but every three months seems a
little excessive.

                Repeated recoverable errors will both slow down writing to a
tape
                considerably and reduce its effective storage capacity.
Perhaps this is
                happening on a handful of your backup tapes.  I suggest
testing this
                hypothesis by reusing the same tape(s) noting how long each
takes to fill
                and, if possible, how much data gets written on each tape.
If some seem
                consistently slower or to handle significantly less data
than other media
                of the same length (note that compression may complicate
determining this)
                then I would get rid of them.

                BTW, this behavior has been around a long time, even on the
old 9-track
                reel drives.  However, unlike DDS, DLT and similar media,
the visible reels
                on 9-track drives could be seen (and usually heard) when
they started
                handling rewrites due to recoverable (aka "soft") errors.  I
suppose this
                is yet another price of progress.
                --
                Jeff Woods
                [log in to unmask] [PGP key available here via finger]