[TUHS] Someone wants to use an exabyte

[Henry Bent]

On Sun, 24 Nov 2019 at 22:37, Larry McVoy <lm at mcvoy.com> wrote:

> On Mon, Nov 25, 2019 at 02:29:02PM +1100, Dave Horsfall wrote:
> > On Mon, 25 Nov 2019, George Michaelson wrote:
> >
> > >I just failed with a Sun DAT drive. Cable and card bought online,
> > >recognized by the mt command, but all it does is eject tapes.
> >
> > They're worse than 9-track tapes, and that's saying something :-)
>
> Really?  Are we talking about those tapes that looked like reel to reel
> audio tapes but bigger?  Like this?
>
> https://www.canajunfinances.com/wp-content/uploads/2013/04/9-Track-Tape.jpg
>
> Because those are 1000x more reliable than an exabyte tape, they just
> worked.  Pretty much no matter what, you can spool up that tape and it
> will read.  30 years later it will read.
>
> Exabyte won't read 20 minutes later.
>

I think that certain amount of the reliability issue, as far as both the
tapes and the drives are concerned, has to do with scale.  Those 8mm
Exabyte tapes (DDS tapes, too) are much thinner and hence more easily
damaged than a large 9 track reel.  If thin tape in a cartridge gets fouled
up past a certain point, forget it, there's no salvaging that cartridge.
If open reel tape gets damaged and you really need what's on it you can
hope that the mechanism can read past the damaged part (a possibility), or
as a last resort you could make a careful splice and then attempt to
retrieve the rest of the data.

One of the other issues, totally independent of tape, is the rubber chosen
by the manufacturers for the drive belts and rollers.  Some rubber, stored
properly, will still be in usable shape after twenty or thirty years.  The
rubber on the rollers of my Sun QIC-150 drive?  A goopy mess which rendered
the drive useless as well as a tape.

But yeah, about 15 years ago I was asked to retrieve some data from Exabyte
8200 tapes that had been written 10 years prior.  I went through three
drives and countless hours of frustration just to read a half-dozen tapes
with some really important information on them.  "Archive format" indeed.

-Henry
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