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
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.
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>