26 Apr
2007
26 Apr
'07
10:13 a.m.
---------------Original Messages:
Date: Thu, 26 Apr 2007 09:45:08 -0700
From: "Chuck Guzis" <cclist at sydex.com>
Subject: Re: DC-600/300XL tape cart observation
On 26 Apr 2007 at 12:16, M H Stein wrote:
Aside from the
issue of archiving them, is it better to leave them
until needed, or should I run
them through a retension occasionally
to prevent some of the problems mentioned recently? Any special
conditions for storage? Well, obviously, a lot depends on the tape formulation
itself. The
job immediately before this one was a DC-6250 written in 1992. Went
without a hitch. The problem tapes are "Scotch" and were written in
1986-87 and are nothing but problems.
To me "archiving" is the key. Copy the
things off to another storage
medium (say, CD-R) and regenerate copies every few
years. It's just
plain foolish to leave things to the mercy of Father Time.
Cheers,
Chuck
---------------Reply:
I'm still curious; assuming any useful data has been archived
and I just want to reuse the tapes some day, what would
maximize the chances of their still being useable? Is heating
them a last-ditch recovery procedure or could it be considered
preventive maintenance? I assume that the 2120s, Travans etc.
are prone to some of the same problems?
Next question:
The DC600s & 615s are Cromemco Cromix+ and UNIX system
and backup tapes; those I have hardware for and they're no great
loss even if they have problems. However, the 300s are for an
Arete/Arix system and I no longer have any hardware that could
read them nor do I know of anyone with an Arix; also, there's the
usual problem that they may have confidential client data on them
along with the system files, so what do I do with them?
I wouldn't mind reusing the tapes but hate to erase them.
Format aside, can a drive meant for DC600s read the lower
coercivity DC300s?
mike
26 Apr
26 Apr
11:49 a.m.
On Thu, Apr 26, 2007 at 02:13:49PM -0300, M H Stein wrote:
Format aside, can a drive meant for DC600s read the
lower
coercivity DC300s?
I've been reading DC300 and 600 tapes just fine in my SCSI
Archive-branded 120MB QIC drive. I don't remember the model number off
the top of my head, but I was talking about it on this list a couple of
months ago.
Pat
--
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12:16 p.m.
On 26 Apr 2007 at 14:13, M H Stein wrote:
I'm still curious; assuming any useful data has
been archived
and I just want to reuse the tapes some day, what would
maximize the chances of their still being useable? Is heating
them a last-ditch recovery procedure or could it be considered
preventive maintenance? I assume that the 2120s, Travans etc.
are prone to some of the same problems?
If the tapes are really old (ca 20+ years), I'd skip reusing them.
Old tape, regardless of the brand, has a tendency to shed oxide to a
greater extent than new tape. This means that you'll be busy
cleaning the heads on your drive more frequently. The tension band
will also have stretched with aging, making the probability of a tape
snarl much greater. I've found that recovering old 2000/2120 tapes
to be significantly more chancy than the bigger DC600 type. DC1000
minitapes are probably even worse.
The DC600s & 615s are Cromemco Cromix+ and UNIX
system
and backup tapes; those I have hardware for and they're no great
loss even if they have problems. However, the 300s are for an
Arete/Arix system and I no longer have any hardware that could
read them nor do I know of anyone with an Arix; also, there's the
usual problem that they may have confidential client data on them
along with the system files, so what do I do with them?
How you want to handle the client files is up to you, but you might
try popping one of the carts into your current drive and using dd to
see if there's anything readable there to copy. I try to do my
recovery in a single pass--run dd and cross my fingers.
Format aside, can a drive meant for DC600s read the
lower
coercivity DC300s?
It depends on the drive and the tape. For most things, I use
Tandberg and Caliper drives, but I've run across a few old tapes that
nothing will read (from ADIC libraries). A look-see with some
magnetic developer shows that they have about double the number of
tracks on them.
Best advice is "try it and see".
Cheers,
Chuck
12:44 p.m.
M H Stein wrote:
I'm still curious; assuming any useful data has
been archived
and I just want to reuse the tapes some day, what would
maximize the chances of their still being useable? Is heating
them a last-ditch recovery procedure or could it be considered
preventive maintenance? I assume that the 2120s, Travans etc.
are prone to some of the same problems?
I'd say heating the tapes should NOT be done periodically.
It should be considered a last-ditch attempt at data recovery.
If you need to heat the tapes, you already know that the
chemistry is breaking down. Heating them is only an attempt
to reduce the effects, I doubt it will stop the process.
30 Apr
30 Apr
9:19 a.m.
So how would you store such carts for the long term?
Sealed can with dessicator, maybe?
Mason jars?
--
jd
The First Commandment for Technicians:
Beware the lightning that lurketh in the undischarged
capacitor, lest it cause thee to bounce upon thine buttocks in a most
untechnician-like manner.
9:09 p.m.
On 30 Apr 2007 at 9:19, jd wrote:
So how would you store such carts for the long term?
Sealed can with dessicator, maybe?
Mason jars?
Seal-a-meal in a dewar of liquid nitrogen,maybe.
The Imation guy got back to me and informed me that, as far as the
factory is concerned, there is no belt. They start with die-cut
doughnuts of a type of sheet polyurethane (proprietary treatment)
and feed them into a jig that "flips" and stretches them to shape.
He said that it was virtually impossible to do this manually.
So, if you've got a belt that holds its shape as a belt, it's
probably too far gone already.
Cheers,
Chuck
1 May
1 May
6:47 a.m.
In article <46365B1B.30368.AD8187F at cclist.sydex.com>,
"Chuck Guzis" <cclist at sydex.com> writes:
The Imation guy got back to me and informed me that,
as far as the
factory is concerned, there is no belt. They start with die-cut
doughnuts of a type of sheet polyurethane (proprietary treatment)
and feed them into a jig that "flips" and stretches them to shape.
He said that it was virtually impossible to do this manually.
So, if you've got a belt that holds its shape as a belt, it's
probably too far gone already.
Would it be possible to setup something like the rig that Al has at
the Computer History Museum for QIC tapes?
Namely, something with analog read heads that are connected straight
to an ADC and signal processed to recover data. You have the tape
brought over the heads at a slower than normal rate, either manually
or with a special motorized rig.
I have a feeling that after 7/9-track tapes that QIC cartridges are
going to be the next major medium that needs reconstruction in this
fashion.
They don't use helical scan on QIC tapes do they?
--
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<http://www.xmission.com/~legalize/book/download/index.html>
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8:15 a.m.
On 1 May 2007 at 7:47, Richard wrote:
Would it be possible to setup something like the rig
that Al has at
the Computer History Museum for QIC tapes?
Maybe, but I think the best thing to start with would be a standard
3-motor setup (one motor per reel and one on the capstan. You'd have
to remove the tape spools from the cartridge, of course, but I
suspect it might be possible to set something like this up with the
works from an old audio cassette drive.
Tracks on a QIC cart are serpentine--they reverse direction at each
tape end. QIC tape tracks tend to be very narrow, which means that if
you're going to use lower tape speeds, a modern head (GMR?) might be
a good choice.
I don't know why it couldn't be done, but we haven't yet seen a lot
of QIC recovery work to justify this yet. I suspect that DLTwill be
the jackpot medium in data recovery.
They don't use helical scan on QIC tapes do they?
Not on the big carts, but I think there were some helical-scan Travan
tapes, weren't there? And there was the Pereos--thank heavens, the
life on that venture was mercifully short.
Cheers,
Chuck
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