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I cannot talk about DDS-4.  Here are some thoughts about DVD.

Currently, DVD is only available as DVD-ROM.  This should change late this
year, or early next year when DVD-R and later, when DVD-RW is released.  I
understand there are 2 different types of DVD-RW being worked on and they
are, of course, incompatible. The whole DVD arena is quite confusing, but
will probably straighten out in a couple of years.  DVD has been ready for
a while, but the bigwigs in Hollywood are the ones who slowed it down
because of copy protection.  (This is also the reason DAT never made it for
music.)  The movies on DVD are really outstanding.  Currently, I have a
LaserDisc and a VCR.  The LaserDisc is far superior to the VCR, but DVD is
even better than LaserDisc, much smaller, and contains far more data.  A
laserDisc contains about 45-50 minutes of the movie, per side.  A DVD can
hold hours of movie and soundtracks.

DVD is supposed to hold up to 9.4 GB.  This is double-sided, double-layer
DVD.

You can see that even at that capacity and whilst DVD is a great
replacement for CD, it is not equivalent to DDS or DLT, especially when the
latter can be part of a library.  The other issue is transfer rate.  We cut
CD-Rs at 2X.  It takes 10 minutes to create a 160MB CD.  That is equivalent
to about 16 MB/minutes.  There are now 4X CD-R drives, which accounts for
about 32 MB/minutes, about the speed of a DDSII, uncompressed.  A DDSIII
device is 10 times faster and has more than double the capacity.  A DLT
device is even faster with even more capacity.

Granted a DVD-R (or whatever rewritable format is produced) may write
faster than a CD-R, but it will not be much faster and it will certainly
not approach the speed of tape drives.

For restores, DVD would be really fast, but DDS and DLT, with the proper
drivers, can access any spot on tape in less than a minute, and face it,
you spend far more time doing backups than doing restores.

Finally media cost is going to be higher for DVD than for DDS or DLT.

Is DVD useless for backups?  Not at all. It just needs to be more focused.
 I would not consider DVD for an enterprise backup device, but I would
certainly look to it for backing up workstations.  On NT, you can create a
bootable CD-R which can contain all the software and OS settings of your
workstation.  I can create a disaster recovery CD which can recreate my
workstation in a few minutes and then I can access the enterprise backup
server(s) and restore my data.  The neat thing about this is that you can
read this CD in virtually any CD-ROM made within the last 3-4 years (which
is the majority of CD-ROMS now in use.)  With DVD-R or rewritable you will
be able to do the same, but with even more data.  Currently a CD-R starts
at $300.  I recommend SCSI, of course, and you can get software that can
write to it easily enough.

Kind regards,

Denys. . .

Denys Beauchemin
HICOMP America, Inc.
(800) 323-8863  (281) 288-7438         Fax: (281) 355-6879
denys at hicomp.com                             www.hicomp.com


-----Original Message-----
From:   Neil Harvey [SMTP:[log in to unmask]]
Sent:   Monday, 24 August, 1998 12:24 AM
To:     [log in to unmask]
Subject:        Re: Re[2]: DDS-3 vs. DLT? Reliability?

Mark

I look forward to seeing the results of your survey. It would be useful
to include some real life backup timings on DDS vs DLT.

Also, I hear rumours of the imminent release of DDS-4, and I an curious
as to the specifications.

One good thing about DAT is the (mostly) upward compatibility of the
media in all drives, i.e. a 60m DAT can still be read and written to in
a DDS-3 drive. I think some madness prevailed when hardware compression
was used in the DDS-2 era. This has enabled one client to avoid
migrating 15million scanned images help offline on DAT's to some other
immature medium.

Which brings me to my next point. Whither DVD?

Regards

Neil




> -----Original Message-----
> From: [log in to unmask] [SMTP:[log in to unmask]]
> Sent: Saturday, August 22, 1998 5:51 PM
> To:   [log in to unmask]; [log in to unmask]
> Subject:      Re[2]: DDS-3 vs. DLT? Reliability?
>
>
> Neil Harvey writes:
>
> >Of course, I cant compare it to DLT, because we don't use DLT.
>
> >Maybe one of the backup vendors could publish a benchmark..........
>
> We have a longer history with DLT than with DDS-3. To my knowledge,
> we've
> not seen any failure with either device to date. That's not to say
> there
> hasn't been any elsewhere, I'm just not aware of it. At Neil's
> request,
> we may do a survey of the offices and customers to see how things are
> faring and report that on our web site. (No guarantees, now, but I'll
> ask the powers that be if this is worth pursuing.)
>
> At ORBiT, we go through a fairly stressful two week period during our
> Q/A cycle. We do beat the heck out of tapes and the drives. But, while
> our tests strive to emulate the real world, they're not 100% effective
> because of test constraints. For example, most of the tests only
> touch some percentage of the leading portion of the tapes. We do have
> tests that write full tapes, go through volume switches, etc., but
> because of the time (and capacity issue) of these tapes, a majority
> of the tests don't. In any event, we'll see tapes go bad from
> excessive
> use before we'll lose a drive. I think in all the time that we've had
> these automated suites running, we've only had a single drive failure
> and that was on a DDS-1 drive. We've never seen a failure with DDS-2
> nor DDS-3 drives in house. And never with DLT.
>
> What's interesting is that our suites exercise these drives darn near
> 24 hours per day for days on end. One would think that we'd see more
> failures because of that. I'm beginning to wonder whether or not
> there's
> a bit of "use it or lose it" going on here. :-)
>
> As Arsinio used to say: "it makes one wanna go 'hmmmmmmmm'".
>
>