daford@watdragon.waterloo.edu (Daniel Ford) (01/18/91)
I have an old reference that states that the life-time of well cared for magnetic tape is about 2 years. Is that the current state of affairs for magnetic tape? What is the expected life-time (i.e., you can still read what you wrote) today? Thanks in advance. Dan Ford CS, UofW
henry@zoo.toronto.edu (Henry Spencer) (01/18/91)
In article <1991Jan17.183902.24474@watdragon.waterloo.edu> daford@watdragon.waterloo.edu (Daniel Ford) writes: >I have an old reference that states that the life-time of well cared for >magnetic tape is about 2 years. We restore off backups that old now and then, and see few problems. Tapes ten years old normally remain readable, although we pay attention to cleaning the tape heads afterward. -- If the Space Shuttle was the answer, | Henry Spencer at U of Toronto Zoology what was the question? | henry@zoo.toronto.edu utzoo!henry
dafuller@sequent.UUCP (David Fuller) (01/18/91)
In article <1991Jan17.191341.12193@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes: >In article <1991Jan17.183902.24474@watdragon.waterloo.edu> daford@watdragon.waterloo.edu (Daniel Ford) writes: >>I have an old reference that states that the life-time of well cared for >>magnetic tape is about 2 years. My recommendations are that you need to commit to the information value of the stuff you're recording before you record it. I recommend that you either use a tape that's been thru a verifier or use a new tape that has been recorded end to end and rewinded a few times to weed out DOAs and shed spare oxide. Most important - storage environment. If the environment changes radically, reread the tape. Store tapes with the tape path VERTICAL. If you store tapes horizontally, the tape pack may slump over time and you'll have a hell of a time reading them. Dave -- Dave Fuller Sequent Computer Systems Think of this as the hyper-signature. (708) 318-0050 (humans) It means all things to all people. dafuller@sequent.com
jzl@micasa.UUCP (Jack Z. Lupic) (01/18/91)
daford@watdragon.waterloo.edu (Daniel Ford) writes: > > I have an old reference that states that the life-time of well cared for > magnetic tape is about 2 years. > > Is that the current state of affairs for magnetic tape? > > What is the expected life-time (i.e., you can still read what you wrote) toda > I have had some 7 inch-reel 1/2in. wide audio tapes for about 22 years and can still play them although I notice that the magnetic coating is coming off more readily than with new tapes. The computer tape should have similar characteristics as audio tape though. ----- Jack Z. Lupic - Scarborough, Ont., Canada {aimed,becker,blister,torag,utdoe}!micasa!jzl
devine@shodha.enet.dec.com (Bob Devine) (01/19/91)
In article <1991Jan17.183902.24474@watdragon.waterloo.edu>, daford@watdragon.waterloo.edu (Daniel Ford) writes: > > I have an old reference that states that the life-time of well cared for > magnetic tape is about 2 years. > What is the expected life-time (i.e., you can still read what you wrote) today? There are many factors in how long a tape is usable : 0. Quality of new tape - a cheap tape is no savings - check quality measurements like number of errors when new, how the tape did on peel adhesion test for oxide break-down, and how it complies with ANSI spec X3.40-1981 (defines the minimal physical properties of an acceptable tape) - tapes are back-coated to reduce static build-up but such tapes the coating causes slippage and leaves a residue on the drive 1. environment of storage - extreme temp swings are bad - contamination (fingerprints, dust, used on dirty drives, etc) - rough handling by operators 2. number of uses - tapes can last fine through up to 500 uses if handled correctly - should retention and clean often (but don't clean too often because it results in extra wear) - start/stop drives are harsher on tapes than streamers just because of the jerkiness causes stretching Soooo, if tapes are handled well and stored properly, they should last two to five years. The only sure gauge of tape reliability is the number of errors a tape generates -- a couple dozen recoverable errors is acceptable, hundreds of errors mean it is new tape time. Bob Devine
buckland@cheddar.ucs.ubc.ca (Tony Buckland) (01/19/91)
In article <1991Jan17.183902.24474@watdragon.waterloo.edu> daford@watdragon.waterloo.edu (Daniel Ford) writes: >I have an old reference that states that the life-time of well cared for >magnetic tape is about 2 years. >Is that the current state of affairs for magnetic tape? >What is the expected life-time (i.e., you can still read what you wrote) today? I have been using tapes for about two decades, and do some consulting on their use. I advise people to think of tapes as reliable for five to ten years, and to mount them at least twice a year to optimize their tensioning. I have had only two tapes actually go bye-bye on me, in neither case with the loss (due to unrecoverable read errors) of more than a record or two, and I have several tapes which have lasted far beyond the five-to-ten-year range. So I'd recommend as a conservative policy: (1) always have a backup tape, i.e. a pair of tapes with identical contents for every collection of data. (2) keep them hanging vertically (to avoid edge damage) in a dust-free environment with controlled temperature and humidity. (3) at least mount and check them every six months. (4) be alert for recoverable read errors, and if they recur or seem to be increasing, replace the tape. (5) if you're a belt-and-suspenders man, or whatever the gender-free equivalent is, replace any tape more than ten years old.
mmm@cup.portal.com (Mark Robert Thorson) (01/19/91)
It seems to me that the "imprinting" phenomenon which slowly destroys magnetic tape recordings could be eliminated by winding two tapes onto a spool headed for storage: one tape holding the data and a second tape with something to diffuse the magnetic field such as nickel metallization. Or maybe a fairly thick tape, say 1 mil, would be enough to separate the tape layers and prevent imprinting. Or maybe just winding a blank tape onto the same spool would be enough. Has any of these ideas been tried?
xanthian@zorch.SF-Bay.ORG (Kent Paul Dolan) (01/20/91)
daford@watdragon.waterloo.edu (Daniel Ford) writes: PLEASE provide a followup group where you will read answers when you cross- post like this! Conversations this far crossposted tend to run on forever, long past any useful purpose, it they don't have followups focused back to a single group. > I have an old reference that states that the life-time of well cared > for magnetic tape is about 2 years. > Is that the current state of affairs for magnetic tape? > What is the expected life-time (i.e., you can still read what you > wrote) today? Your references are far too conservative; probably you were reading a tape vendor's comments. Of course they'd like you to be replacing tapes every two years. I made this part of an 18 month study of _very_ long term data storage for the Commerce Department back in 1978; even then, you could keep a good quality magnetic tape readable for up to 20 years if you took several precautions; others have talked about storage and cleanliness of both tape and tape readers, and retensioning the tape. I'll just add that tape that stays wound for a very long time can have data write through from one layer to the next; it is important to rewind at least every three months just to prevent this write-through by subtly realigning the layers. While you're doing that, you might as well read the data to verify it's integrity, and make new tapes and backups if recoverable read errors start to show up. Kent, the man from xanth. <xanthian@Zorch.SF-Bay.ORG> <xanthian@well.sf.ca.us>
bender@oobleck.Eng.Sun.COM (Michael Bender) (01/20/91)
In article <38204@cup.portal.com> mmm@cup.portal.com (Mark Robert Thorson) writes:
->It seems to me that the "imprinting" phenomenon which slowly destroys
->magnetic tape recordings could be eliminated by winding two tapes onto
->a spool headed for storage: one tape holding the data and a second tape
->with something to diffuse the magnetic field such as nickel metallization.
->Or maybe a fairly thick tape, say 1 mil, would be enough to separate the
->tape layers and prevent imprinting. Or maybe just winding a blank tape
->onto the same spool would be enough. Has any of these ideas been tried?
Well, I was reading in an old issue of Videography that they recently found
some "lost" episodes of Fred Astair from the late 50's on COLOR videotape,
which they thought to be the first commercial/broadcast use of color
videotape. The problem was, they couldn't find the machine that was used to
record the tape; it was a 2" quad, but one that had been extensively modified
by RCA engineers, and was no longer in existance. The people restoring the
tapes finally got through to some of the RCA engineers that had done the
modifications in the 50's, and via schematics, notes, and circuit simulation
(!) software, were able to, after about 6 months, convert an old Ampex 2"
quad to read the Astair-format tapes. They said that the tapes were
remarkably well preserved, being kept in a vault and stored properly, and
the images that they got were surprisingly good, considering the era in
which they were recorded. They transferred the old tapes to D-2 and did a
bunch of clean up and editing in that format. Pretty neat stuff, huh? It
would be a bear if everytime you wanted to bring one of your tapes over to
your friend's house for viewing, you had to re-engineer their VCR!!
mike
--
Won't look like rain, Won't look like snow, | DOD #000007
Won't look like fog, That's all we know! | AMA #511250
We just can't tell you anymore, We've never made oobleck before! | MSC #298726krboyce@athena.mit.edu (Kevin R Boyce) (01/23/91)
mmm@cup.portal.com (Mark Robert Thorson) writes: >It seems to me that the "imprinting" phenomenon which slowly destroys >magnetic tape recordings could be eliminated by winding two tapes onto >a spool headed for storage: one tape holding the data and a second tape >with something to diffuse the magnetic field such as nickel metallization. >Or maybe a fairly thick tape, say 1 mil, would be enough to separate the >tape layers and prevent imprinting. Or maybe just winding a blank tape >onto the same spool would be enough. Has any of these ideas been tried? The thick tape is called "back-coated", and is used in the industry. Actually, I get my knowledge of this from a college radio station (soon to be 15,000 watts at 600 feet!), where the only tape we could afford was stuff that got sent to us free with programs on it, so I don't know how common back-coated tape really is. I suspect it is the most commonly used type. It is about 1 mil thick, normally, and certainly is much more immune to print-through, though not completely. Also easier to mark with a grease pencil for splicing. Eewww, physical analog splices! -------- Kevin boyce@amo.mit.edu War. Good God, y'all. Absolutely Say it again... HUH! What is it good for? NUTHIN!
bcollins@axion.bt.co.uk (bill collins) (02/04/91)
I recently read an old copy of "New Scientist" (22 Sep 90), which talked
about the problems facing master audio tapes, although I guess that there
could be related problems to computer tapes ...
The article mentions, in particular, the use of polyurethane as a binder
on tapes (the "glue" that holds the magnetic iron oxide onto the polyester
film base). The polyurethane absorbs water, and releases an acid which
produces gummy residues on the tape. The tape then sticks and judders in
the tape recorder.
Apparently, this is a problem mainly for tapes produced between the
mid-70's and mid 80's (although this binder was used as early as 1962).
Problems have been found recently with studio quality tapes of that era,
but could affect any tape produced in that period. Ampex are named as
one make which is known to suffer from this problem (quarter and 2 inch
tapes); whilst Agfa are reported as having had problems only 3 years ago,
after a change of chemical mix.
There is a way of stabilising affected tapes (baking them in an oven
for up to 6 days at temperatures up to 50 C.), which will allow them to
be transferred onto more stable stock. However, this is not a trivial
problem .... EMI's Abbey Road recording studios are reported to have
around 280,000 tapes in their archives !
I don't think that this proves very much, except that long-term storage
of any material is open to doubt (and may not be predictable). In the
main, you hope that you never need to go back into the archives.
"Use it or lose it" seems to be the appropriate motto here ...
Regards,
Bill
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+----------------------------------------------------------+kludge@grissom.larc.nasa.gov ( Scott Dorsey) (02/05/91)
In article <1991Feb4.100546@axion.bt.co.uk> bcollins@axion.bt.co.uk (bill collins) writes: >The article mentions, in particular, the use of polyurethane as a binder >on tapes (the "glue" that holds the magnetic iron oxide onto the polyester >film base). The polyurethane absorbs water, and releases an acid which >produces gummy residues on the tape. The tape then sticks and judders in >the tape recorder. There are a few tapes which have had binder problems, but the vast majority of tape problems from that era are due to backcoating lubrication. Whale-oil derivatives were very popular for tape backcoating, and when it was no longer available, petroleum derivatives began to be used. Many of the petroleum based lubricants break down and cause the backcoating to become a slimy scum which sticks to the heads and capstan, tears off the oxide coating, and generally makes a mess of things. Heating the tape to stabilize it for one playing is possible, as are silicone treatments and use of various solvents. A lot of master tapes and instrumentation materials were lost. Acetate tapes which are not usually backcoated don't have this problem (although they do tend to become very brittle with age). In any event, I have tapes (actually paper with oxide coating) from 1938 which are in playable condition, and other tapes that are ten years old (recorded on early seventies Scotch 208) which are not possible to salvage. --scott (who has altogether too many tapes in his house)
kludge@grissom.larc.nasa.gov ( Scott Dorsey) (02/11/91)
In article <38204@cup.portal.com> mmm@cup.portal.com (Mark Robert Thorson) writes: >It seems to me that the "imprinting" phenomenon which slowly destroys >magnetic tape recordings could be eliminated by winding two tapes onto >a spool headed for storage: one tape holding the data and a second tape >with something to diffuse the magnetic field such as nickel metallization. >Or maybe a fairly thick tape, say 1 mil, would be enough to separate the >tape layers and prevent imprinting. Or maybe just winding a blank tape >onto the same spool would be enough. Has any of these ideas been tried? The BBC once tried archival storage of tape in a similar way. They would wind a thick paper leader and a tape together on a reel so that the layers were seperated. This eliminated print-through almost completely, but it dramatically increased the storage space. Print-through isn't that much of a problem with modern tapes if you use 1.5 mil stuff. With thinner tapes it can be a serious problem. --scott