Subject: Tape media

From: Gunther Schadow <[email-masked]>
Date: Sat Mar 22 21:55:01 2003

Hi,

so I sorted through my last weekend's bait, hooked up my new HSZ40
(with 50 GB in 4 StorageWorks boxes plus all sorts of tape drives,
TSZ07, TLZ07, TZ68, and ~88) to my PC for FreeBSD. It's so much
fun to read a 9-track reel from a FreeBSD PC (just too bad it doesn't
have a transparent top cover to show off the reels).

I have bulk-erased a bunch of TK50 tapes in the hopes that they
would work as DLT III and IV tapes as well, but these drives
still went into write-protect mode. Does anyone here know details
about the DLT media? I mean it is a well-known fact (and I proved
it to myself many times) that CompacTape I works just fine as
CompacTape II. So why not as III and IV? Is it really the tape
or might it be some notches on the cassette that are used to
code the kind of tape?

The problem is I didn't get any tape media for my nice DLT tape drives
and this stuff is so darn expensive if bought new. Any ideas?

regards,
-Gunther

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From: "Jerome H. Fine" <[email-masked]>
Date: Sat Mar 22 22:35:00 2003

>Gunther Schadow wrote:

> and this stuff is so darn expensive if bought new. Any ideas?

Jerome Fine replies:

Memorex used to have a list of all of the physical characteristics
of CompacTape / DLT tapes.  I can't remember any of the actual
numbers, but I do remember the key information you require.

CompacTape I and CompacTape II were completely identical
in every detail - except for for the colour of the name on the case.
Usually The "CompacTape" label was brown;  the "CompacTape II"
was usually blue.  Oh yes, DEC charged a fair bit more for the tape
with the blue label.  Both the TK50 and the TK70 used these tapes.
However, once a given drive started to write on a blank tape, it was
not possible to switch the tape to be written by the other drive.  In
particular, the TK70 could read tapes written by a TK50 drive, but
the TK70 would immediately WRITE  PROTECT itself as soon as
the tape was interested into the TK70.  A bulk erase is required to
allow switching the tapes between the TK50 and the TK70 - as
your have already discovered.

As for the DLT III media, the physical characteristics were substantially
different from the CompacTape media.  I am quite sure that the drives
which use the DLT media are unable to use the CompacTape media.
Likewise, the TK50 / TK70 drives are unable to use the DLT media.

DLT IV media are very different again from DLT III media.

Sincerely yours,

Jerome Fine
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From: Jeffrey Sharp <[email-masked]>
Date: Sun Mar 23 09:41:00 2003

On Saturday, March 22, 2003, Gunther Schadow wrote:
> It's so much fun to read a 9-track reel from a FreeBSD PC (just too bad it
> doesn't have a transparent top cover to show off the reels).

Now that would be an interesting mod, a good way to poke fun at all these
people nowadays that are putting plexiglass windows on their PC cases!

-- 
Jeffrey Sharp

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From: [email-masked] (Tony Duell)
Date: Sun Mar 23 13:22:00 2003

> was usually blue.  Oh yes, DEC charged a fair bit more for the tape

This convention -- brown for low-capacity, blue for high capacity -- was 
used on other DEC media of course (RL01 and RK06 packs have brown 
handles, RL02 and RK07 packs have blue handles). Although in that case 
there are differences other than the colour.

-tony

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From: "Jerome H. Fine" <[email-masked]>
Date: Sun Mar 23 15:31:00 2003

>Tony Duell wrote:

Jerome Fine replies:

I would not mind at all if there were physical differences that
were required by the TK70.  But when the ONLY two differences
were the "II" after the name "CompacTape" and the price, I
tend to think that perhaps DEC was ...

In addition, I also heard that in some cases, the TKQ50 controller
was unable to use the drive in a satisfactory manner.  In those cases
the TKQ70 controller was needed for the TK50 drive.  I have
actually tried the TKQ70 / TK50 combination and it works quite
well.  It is still the TK50 drive with only the capacity of the TK50,
but it does operate a bit faster.

I realize that the TK70 drive arrived years after the TK50.  Does
anyone know if the device drivers that can use the TK50 can always
use the TK70 as well?

Sincerely yours,

Jerome Fine

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From: Gunther Schadow <[email-masked]>
Date: Sun Mar 23 19:44:00 2003

> tend to think that perhaps DEC was ...

Yes, in the case of ComapcTape I vs. II DEC simply ripped people,
but that's normal in the business. I am just amazed about how
much corporate customers are willin to let themselves be ripped
off by the Computer industry. How about a rack railkit for a
$10000 FibreChannel switch for which they charge an additional
$300 (for a few pieces of sheet metal with screws!)

> but it does operate a bit faster.

Yes, I tried it to in order to write a TK50 tape for my uVAX-II
from my VAX6k. Now that I write this, I never really tried if
writing to the /dev/mt2l device would have done the trick with
writing TK50 format on TK70 drive. I doubt it would.

> anyone know if the device drivers that can use the TK50 can always

For all I know it's MSCP, so the driver may not be different.

-Gunther