On Fri, 6 Sep 2002, Brian Jonnes wrote:

>I will be looking to get a new tape drive, but am not very familiar with the
>current technology. I have heard of DDS, DAT and have used Travan. As far as
>I'm concerned, the Travan is out of the question, 'cause the tapes are so
>expensive (and apparently they are now obsolete?).

As Gene Heskett indicated elsewhere in the thread the appropriate tape
technology depends on your budget and intended use.

DAT/DDS is perfect for a home user.  Far better than QIC/Travan ever was
in terms of the price to performance ratio.  However, I wouldn't
currently sink any money into it as a new solution for
commerical/business use.  Sony has announced that DDS4 is the end of the
road for DAT based backup technology.  They're transitioning entirely to
AIT.

I've been using AIT for going on three years now and I've been extremely
happy with it.  It's more expensive than DAT formats, but it's getting
cheaper.  I've used AIT1 for the past three years and am currently
transitioning to AIT3 technology.   AIT1 is 35GB native capacity, AIT2
is 50GB and AIT3 is 100GB native capacity.  With the release of AIT3
drives and tapes the prices on AIT1 are falling to where they can begin
to compete with DDS4 -- which is limited to 20GB.  Plus AIT drives can
stream at or near the speed of a conventional hard disk in my
experience.  Amanda does an excellent job of keeping the drive busy via
taper.

DDS is a 4mm tape format and AIT is an 8mm tape format.  Both of these
are rather small form factor cartridges which make for easy storage.
Both technologies achieve their capacity through helical scan technology
and use double-reel cartridges.

LTO is currently positioned to replace DLT in the high-end tape market.
LTO stands for linear tape-open and the cartridges contain a single reel
of tape which is wound onto a reel in the drive instead of remaining in
the cartridge.  Linear tape technologies like this achieve their density
by cramming a whole buncha tape into a really big cartridge, leaving no
room for a second reel.  I get the willies at the thought of my tape
being wound out of the cartridge and into the drive, but it seesm to
work fairly reliably.  It it's "high-capacity" format, Ultrium, LTO
currently supports tapes of 100GB or 200GB native capacity.  Personally
at the prices they want for those suckers I'd just as soon buy a 100GB
native capacity AIT3 drive with a fat stack of tapes.  The AIT3
cartridges are small and easy to store and if you're planning to use
amanda -- where you likely rewrite the tapes every couple of weeks --
it's hard to beat AIT's Advanced Metal Evaporate tape medium and the
fact that you can actually afford to replace AIT tapes when, not if, you
have one wear out.

Also, Sony will release SAIT-1 towards the end of this year which is
their own single-reel cartridge format -- though they're sticking with
helical scan instead of linear tape technology.  SAIT-1 will debut at
500GB native capacity in a cartridge whose size is equivalent to that of
an LTO cartridge.  They're roadmap takes them up to SAIT-4 at 4GB native
capacity by 2010.  Crazy man.

Hope I've provided some food for thought,

-- 
Brandon D. Valentine <bandix AT structbio.vanderbilt DOT edu>
Computer Geek, Center for Structural Biology

"This isn't rocket science -- but it _is_ computer science."
        - Terry Lambert on current AT FreeBSD DOT org.