jacobo@megatest.UUCP (02/18/87)
The question is: Is it safe to reuse mag tapes for important data or
should we use brand new tapes when storing critical information?
Would someone have a strong feeling, based on experience or data, one way
or the other? I know that the whole idea of using mag tapes is that you
can reuse them a good number of times, but I have also heard people
saying that valuable info should go on virgin tapes.
Any comments would be greatly appreciated. Please mail to me directly.
Thanks.
Jacobo
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PHONE: (408)437-9700 x 3171ems@apple.UUCP (02/22/87)
In article <1058@megatest.UUCP> jacobo@megatest.UUCP (Jacobo Bulaevsky) writes: > > The question is: Is it safe to reuse mag tapes for important data or > should we use brand new tapes when storing critical information? > > Would someone have a strong feeling, based on experience or data, one way > or the other? I know that the whole idea of using mag tapes is that you > can reuse them a good number of times, but I have also heard people > saying that valuable info should go on virgin tapes. > > Any comments would be greatly appreciated. Please mail to me directly. > Thanks. > I think this topic is of general enough concern that replies should be posted. I'm interested. WAR STORY: Once upon a time a company I worked for used virgin tapes for the important stuff. Then we started having a strange problem. Some tapes would be fine for a while, then after being stored for a few days would be unreadable. This was never completely solved, but was believed to be due to a batch of questionable tapes. MORAL: Use relatively new, but not virgin tape for really important things. You want to get past any 'infant mortality' problems and use a proven product. Avoid heavily used tape, as it can begin to develop problems. We did one of our daily backups on a virgin tape, then took the oldest tapes out to be 'keepers' This gave the tape a few uses before something critical went on it. If we hit a bogus virgin tape, it was only one days worth that was lost, the prior day having been done on a veteran tape. Of course, we had to check the backups periodically ... It takes a LOT of uses to wear a tape out. I would guess somewhere in the hundred range or so... -- E. Michael Smith ...!sun!apple!ems 'If you can dream it, you can do it' Walt Disney This is the obligatory disclaimer of everything. (Including but not limited to: typos, spelling, diction, logic, and nuclear war)
res@ihlpl.UUCP (02/24/87)
In response to: > > The question is: Is it safe to reuse mag tapes for important data or > > should we use brand new tapes when storing critical information? > > > > Would someone have a strong feeling, based on experience or data, one way > > or the other? I know that the whole idea of using mag tapes is that you > > can reuse them a good number of times, but I have also heard people > > saying that valuable info should go on virgin tapes. > > It takes a LOT of uses to wear a tape out. I would guess somewhere in > the hundred range or so... While working on a tape controller for the AT&T 3B5 and 3B15 computers we used one tape for soak testing for many days. All told, I believe it racked up on the order of 500 hours of use without exhibiting a reproducible failure (we had to retire it when it got knocked from atop a machine and the reel ended up in three pieces. The tape was Graham Ultimag -- expensive, but it did the job for us very nicely. On the other hand, our Lab Administration people once got a batch of tape that the Purchasing Department must have got such a deal on. Ten passes over the head and the stuff was ready to be scrapped. After trying to use it for a short while they shipped it back to the distributor and got some of the stuff that they ordered in the first place. So, how long a tape will last will depend on the initial quality (there are lots of good brands out there -- Graham being one of my personal favorites, but not the only one by any means) and on the care given the tape when you use it. Rich Strebendt ...!ihnp4!iwsl6!res
falk@uxc.cso.uiuc.edu.UUCP (02/24/87)
In article <1058@megatest.UUCP> jacobo@megatest.UUCP (Jacobo Bulaevsky) writes: > > The question is: Is it safe to reuse mag tapes for important data or > should we use brand new tapes when storing critical information? > > Would someone have a strong feeling, based on experience or data, one way > or the other? I know that the whole idea of using mag tapes is that you > can reuse them a good number of times, but I have also heard people > saying that valuable info should go on virgin tapes. > In my experience, brand-new tapes tend to have *more* problems than "slightly used" ones. At a former job, I ended up doing a rather large "study" of this phenomenon after we began experiencing problems with recovering backups from once-written tapes. One of the things that I found was that brand new tapes tend to be dirtier than slightly-used ones (excess iron-oxide that came off in the tape drives), so I instituted a policy of cleaning each new tape before use. That eliminated some of the potential failures, but not all. By trial and error it was noted that tapes that had been written and read at least once before had a better "recovery rate" than once written tapes- not sure why except perhaps that you are weeding out the bad apples at that point. If you think about it, would *you* want to trust valuable data to an untested medium? As far as maximum usage, theoretically, you ought to be able to reuse tapes into the hundreds or thousands of times. Improper handling, poorly adjusted tape drives, environmental disturbances, etc., guarantee that number to be reduced significantly, probably down to 50-100. While we were going thru this mess, before we isolated the problem, I had some tape manufacturer reps come down and they told me that they do verification testing of some tapes from each batch by writing and reading tapes n-times until they fail, hence, the above numbers. Connie Falk UUCP: {ihnp4,pur-ee,convex}!uiucdcs!uiucuxc!falk ARPANET: falk%uiucuxc@a.cs.uiuc.edu CSNET: falk%uiucuxc@uiuc.csnet ICBM: 40 07 N / 88 13 W US Mail: Univ of Illinois, CSO, 1304 W Springfield Ave, Urbana, IL 61801 AT&T: 217-333-8050
rbj@icst-cmr.arpa (02/25/87)
From: Jacobo Bulaevsky <jacobo@megatest.uucp>
Date: 18 Feb 87 01:23:41 GMT
The question is: Is it safe to reuse mag tapes for important data or
should we use brand new tapes when storing critical information?
No. You should mail all your used tapes to me :-) Seriously, there is even
a case *against* using virgin tapes. The deflowering process stretches the
tape and rubs some of the oxide off. You might do better writing the
data twice, or at least running a program that writes until EOT and
then rewinds. You could even run a verification pass for crucial tapes.
Of course, we do nothing of the sort. I am merely speculating, altho
those little cartridge tape drivers often have a `retension' command
which fast forwards and then rewinds. Good luck.
(Root Boy) Jim "Just Say Yes" Cottrell <rbj@icst-cmr.arpa>
Help! A 900 foot tall vision of Dennis Ritchie told me
that if I don't get my 4.3 BSD tapes by March I'll die!jnp@calmasd.UUCP (02/26/87)
> jacobo@megatest.UUCP (Jacobo Bulaevsky) writes: > The question is: Is it safe to reuse mag tapes for important data or > should we use brand new tapes when storing critical information? In the broadcast field (yes - I know that the recording techniques are different - but the media isn't) it is generally accepted that used but not worn-out tapes are best for archival storage. Has something to do with the original-factory-fresh erasing done, and that it takes several recording erasing cycles to make the tape really "take" a recording well. I have heard this arguement applied to Video tapes as well. My guess is that - at least to some extent - it would be true for digital tapes as well. -- These opinions are solely mine and in no way reflect those of my employer. John M. Pantone @ GE/Calma R&D, Data Management Group, San Diego ...{ucbvax|decvax}!sdcsvax!calmasd!jnp jnp@calmasd.GE.COM
greg@utcsri.UUCP (Gregory Smith) (03/03/87)
In article <1861@ihlpl.ATT.COM> res@ihlpl.UUCP writes: >> It takes a LOT of uses to wear a tape out. I would guess somewhere in >> the hundred range or so... Another issue, if you are using old tapes, is dirt. I have only worked with 'real' (reel? :-) ) magtape once, on a newly installed previously owned PDP-11/45. We had a big box of tapes, also previously owned. One of them had so much scum on it that, after about half the tape was written, the scum buildup on the head was causing the tape to stick. It starting making this 'pop pop pop pop pop' noise, as the capstan pulled the tape free, only to have it get stuck again. I don't imagine there was a lot of useful data being written to that tape. The first time this happened, we figured the dirt might have already been on the head, so we cleaned the head and tried again. Same result. We didn't try yet again. I have no idea how a tape could get that dirty. Possibly it was used on very dirty equipment, or maybe the oxide binder had softened for some strange reason. -- ---------------------------------------------------------------------- Greg Smith University of Toronto UUCP: ..utzoo!utcsri!greg Have vAX, will hack...
mangler@cit-vax.UUCP (03/04/87)
In article <176200004@uxc.cso.uiuc.edu>, falk@uxc.cso.uiuc.edu writes: > ... would *you* want to trust valuable data to an untested medium? If the data is valuable you should make multiple copies. No media is perfect. Once you understand this, it becomes clear that the tape drive used to make the copies is more critical than the tapes (all backup copies made on a broken tape drive will be unreadable). Don Speck speck@vlsi.caltech.edu {seismo,rutgers,ames}!cit-vax!speck
WELTY@ge-crd.arpa (WELTY RICHARD P) (03/05/87)
Date: 5-MAR-1987 10:46 From: Richard Welty Sender: WELTY Subject: Re: Re: Should we reuse mag tapes? To: info-unix@brl.arpa@smtp -------- --------
WELTY@ge-crd.arpa (WELTY RICHARD P) (03/05/87)
Date: 5-MAR-1987 13:48 From: Richard Welty Sender: WELTY Subject: Re: should we reuse mag tapes? To: info-unix@brl.arpa@smtp -------- I see that my previous message was trashed by a mailer somewhere -- here is an attempt to reconstruct it: > System Mangler <mangler@csvax.caltech.edu> writes: >If the data is valuable you should make multiple copies. No media >is perfect. Once you understand this, it becomes clear that the >tape drive used to make the copies is more critical than the tapes >(all backup copies made on a broken tape drive will be unreadable). In fact backup copies made on a misaligned tape drive may be readable, and tapes made elsewhere may not. In addition, if a FE fixes the drive and realigns it, old backup tapes may cease to be readable. Whenever a drive is installed, always double check the alignment. -- Richard Welty (welty@ge-crd.arpa) --------