*BSD News Article 80471


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From: ekilroy@orbitsw.com (E.A. Kilroy, III)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: scsi tape recommendations
Date: Sat, 12 Oct 1996 08:24:43 GMT
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jlm@caamora.caamora.com.au (jonathan l michaels) wrote:


>this leaves me with a freebsd box without a tape drive, does anybody have any
>recommendations. something along the lines of the tandberg would be nice, i
>have a library to maintain so a qic-525 type that would read and write one or
>two gig format would be ideal. though, i'd be interested to hear from people
>who have used the sony dats (4 gig uncompressed).

Hi.  I'm using HP SCSI DDS (DAT) drives and they really are
plug-n-play.  I've got DDS-1 non-compressing (90m=2GB), compressing
(90m~=4GB), and DDS-2 compressing (120m~=8GB) drives that I swap back
and forth from HP3000, HP9000,  NTServer, and FreeBSD depending on
what I need at the time.  Lots of data in an itty bitty space, but a
word of warning:

  NEVER TRUST ANYTHING IMPORTANT TO ONLY ONE DDS TAPE
  AND ALWAYS VERIFY THE TAPE AFTER WRITING IT.

That's more than a word, isn't it?  I don't know if QIC, 8mm or others
are much better or worse,  but DDS (DAT) has got to be near the bottom
of the pile.  The HP drives are some of the best and do automatic Read
After Write (RAW) which some drives don't.  I think the basic problem
is that the DDS format RELIES on error correction logic while WRITING
instead of only as an emergency recovery method for reading.  Add to
this that I haven't seen a drive/driver yet that reports any type of
write retry info back to the system like used to be available on
9-track (at least HPIB bus drives) and you've got data loss just
wating to happen; and it does.  I've seen  DDS tapes with 10% RAW
errors while creating a tape and nobody knows (stats are actually kept
at the front of each tape; that's part of difference between old DAT
and DDS Media Recognition).  I specifically saved one for grins and it
wasn't readable a month later!!!  It had verified too!

In general, the DLT's might be the best format these days, but I can't
prove that; just started using them, and they're way too expensive for
personal use anyway, but they FLY!

Well, enough out of me.  Don't discount DDS because of what I've said,
just be aware of what you are dealing with.  I backup machines every
day w/DDS drives.  Unless you MUST have the capacity, I'd stay away
from the new 120m DDS2 drives until they've been in use long enough to
tell what the media reliability is like.

>can anybody recommend a real simple solution, you know just set the jumpers to
>id4 plug it into the scsi chain and reboot the machine.

>regards ... jonathan

>EMail: jlm@caamora.com.au
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