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From: Jeff Liebermann <jeffl@comix.santa-cruz.ca.us>
Subject: Re: DVD-RAM
Date: Wed, 25 Dec 2002 16:35:11 -0800
References: <3e05e9aa$0$1396$2c3e98f8@news.voyager.net> <H7JHMo.ypn@wjv.com> <au7100$1kl$1@pcls4.std.com> <3e07273e$0$1432$2c3e98f8@news.voyager.net> <3e07b30e$0$79555$8eec23a@newsreader.tycho.net> 

On 24 Dec 2002 01:06:22 GMT, spcecdt@deeptht.armory.com (John DuBois)
wrote:

>Helical-scan drives have always been problematic.

I hate to agree here but I've had far too much entertainment value
from various DDS flavours to consider them reliable.  I think I've hit
just about every problem possible.

1.  The media doesn't last.  100 write+verify passes and they're
toast.

2.  Short head life.  3ea identical Sony SDT-9000 (DDS-3) drives at
different locations.  Lifetime was 1800hrs, 4000hrs, and something
like 7000hrs.  The heads in the 1800hrs was apparently killed by a
dusty environment.

3.  Incompatible tape formats between firmware versions.  I got lucky
and was able to find an old firmware tape loader which allowed us to
read the old tapes.

4.  Mechanical damage due to jammed tapes.  This seem to be happening
with every vendors drives.  No matter how careful one seems to be,
there seems to be one tape every 3 months that gets de-spooled inside
the drive.  For HP, punch the eject button 3 times and wait 30
seconds.  Then, grab the tape with a hemostat and pull.

5.  Reliability on restore is dubious.  Although we do a bit level
verify on every backup, I still get restore failures.  The issue seems
to be head wear.  The older the head, the more restore errors.  If the
drive has changed (even with the same model), it's a crap shoot.

6.  Mysterious driver hang issues that only happen with DDS.  With
DDS, I sometimes get an unkillable tape related process that requires
a power cycle to recover.  Remote power cycles in the middle of the
night are no fun.  Strangely, when I switched several customers to AIT
and DLT-8000, the hangs apparently have gone away.

7.  DDS-2 tapes on a DDS-3 drive seems to be a challenge.  Sometimes
it works, usually it doesn't.  The docs say that it should be possible
and I don't see much of a reason why I'm having problems.  As usual,
it works when I don't need it, and fails when I'm trying to recover
some ancient archive file from a year old tape.  I now carry an
external TapeStor 6000 (DDS-2) drive in my truck.

8.  The juke boxes are junk.  I have an HP-12000 DDS-2 juke box in my
office for repair.  Basically, it's an turret autoloader that feeds an
ordinary DDS-2 (C1533A) drive.  It jammed up so badly that I had to
disassemble the box.  In the process, I discovered that the connector
between the turret and the drive had only 1/4" of slack, and would rip
the solder pads off the drive instead of disconnecting when pulling
the case apart.  I've also been into a Sony TSL-7000 juke box which
has a brick like cartridge for juggling tapes.  It takes longer to
initialize and juggle the tapes than to run the backup.  It also fails
with mysterious drive errors that even an authorized Sony repair shop
couldn't decode.  A replacement drive did the same thing.

There are others but I don't wanna try to remember them.  I've almost
given up on DDS and have switched several customers to DLT-8000 and
Seagate Sidewinder AIT (200GB/tape).  Both are quite reliable and have
required no attention since installation about 15 months ago.
However, media costs are outrageous.  I still have some DDS-3 drives
in service and am waiting for the next disaster or head wear failure,
to justify a replacement.

I've also done some experiments with backup up to a DVD burner
(DVD+RW).  However, it was attached to Windoze 2000 box that backed up
the data directories on an OSR5 box over the network using SAMBA mount
points.  Speed was tolerable using FDX 100baseT thru an HP4000
ethernet switch.  Gigabit ethernet would have been better, but
3.2v5.0.5 doesn't support gigabit.  /root and /stand were backed up
using a compressed cpio file created before the actual backup was run.
No experience with DVD burners directly connected to the OSR5 box.

Oh yeah, happy holidaze.

-- 
Jeff Liebermann  150 Felker St #D  Santa Cruz CA 95060
(831)421-6491 pgr  (831)336-2558 home
http://www.LearnByDestroying.com   WB6SSY
jeffl@comix.santa-cruz.ca.us   jeffl@cruzio.com

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