Xref: utzoo comp.sys.dec:3551 comp.misc:9450
Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!decwrl!hayes.fai.alaska.edu!acad2.anc.alaska.edu!fnddr
From: fnddr@acad3.fai.alaska.edu (RICE DON D)
Newsgroups: comp.sys.dec,comp.misc
Subject: Re: Exabyte (8mm) versus DAT (4mm)
Message-ID: <1990Jul9.230745.26256@hayes.fai.alaska.edu>
Date: 9 Jul 90 19:48:00 GMT
References: <9007061713.AA01816@stc06.CTD.ORNL.GOV> <1881@proa.SV.DG.COM> <13113@cbmvax.commodore.com>
Sender: usenet@hayes.fai.alaska.edu (J Random USENET)
Reply-To: fnddr@acad3.fai.alaska.edu
Organization: University of Alaska Fairbanks
Lines: 44
News-Software: VAX/VMS VNEWS 1.3-4

In article <13113@cbmvax.commodore.com>, grr@cbmvax.commodore.com (George Robbins) writes...
>In article <1881@proa.SV.DG.COM> gary@proa.SV.DG.COM () writes:
>> In article <9007061713.AA01816@stc06.CTD.ORNL.GOV> de5@ornl.gov (Dave Sill) writes:
>> >DEC seems to be pushing DAT's, and argues that they're inherently
>> >better since they were designed to record digital data, whereas 8mm is
>> >an analog video format.
>> 
>> Why wasn't this sent to rec.humor.funny?  This is the funniest thing I've
>> seen on the net this year.  Did someone actually say that?
> 
>> Digital Audio Tape was designed to record SOUND.
> 
>Yes, *digitized* sound, whereas 8-MM is designed to record analog video.
> 
>The differences between the electronics of a transport designed to record
>in a saturated digital mode vs a fairly linear analog mode may be significant.
> 
There was a long article in one of the design rags a couple of months ago about
4mm vs. 8mm, from the standpoint of coding methods.  It claimed that 4mm uses
the same error correction methods designed for human-listener audio playback,
while 8mm uses algorithms specially tuned for computer data storage.  The
conclusion was that the 8mm algorithms were far superior for archival
applications.  Since this article was written by an Exabyte engineer, we can
be sure it is unbiased and accurate, right?

But the point of the original posting, I think, is whether 8mm or 4mm is the
better overall choice for backups.  I'm very interested in this question
because I'll be buying one or the other shortly and haven't really decided
which.  I've seen others post similar queries but I haven't seen an
enlightening followup or summary.

The 4mm seems to cost substantially more (~1.5x) that the 8mm for initial
hardware.  Currently, 4mm stores half as much as 8mm per tape.  This would
seem to make 8mm the best buy.  However I've seen enough questions about
8mm reliability to make me wonder.  How much downtime do 8mm users see?
Are problems due to the exabyte mechanism itself, or the supporting hardware
or software?  Has anyone been using 4mm long enough to make a meaningful
statement about its reliability or overall impressions?  If this has been
addressed in print somewhere, references would be appreciated.

Thanks,
Don Rice
fnddr@acad3.fai.alaska.edu
fnddr@alaska (bitnet)