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
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...
tooch@guppy.UUCP (03/10/87)
>> The question is: Is it safe to reuse mag tapes for important data... > ...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. Nonsense. Every single pass degrades tape through friction and tension (shuttle on a poorly designed transport is hell on tape). For that matter, the heads get worn and/or clogged also. Oxide comes off, the substrate stretches, etc. Each pass brings the tape closer to death, and statistically increases chances for droupout (the bugaboo of digital tape) and so forth. In the world of magnetic recording, unlike life, the first time is not only the best, it's also completely forgettable. With that said, I must also point out that the degradation experienced each pass varies depending on tape and transport, but by and large the first (say) dozen passes on a GOOD recorder SHOULD produce unnoticeable changes in the quality of a GOOD tape. This is as I heard it at Ampex. 3M might tell you differently. --Mike Tuciarone tooch@sun
ken@rochester.UUCP (03/11/87)
|In the world of magnetic |recording, unlike life, the first time is not only the best, |it's also completely forgettable. That is what logic would lead one to expect and I agree with the reasoning behind this conclusion. However, my experience has been that running a new tape through the drive once, recording dummy data, makes it more amenable to recording the second time. I know, it doesn't make sense. Anyway it is a good idea to run a fresh tape through once to check for dropouts and to unstick the tape, if it has been in storage a while. Ken
chris@mimsy.UUCP (03/13/87)
>>In the world of magnetic recording, unlike life, the first time is >>not only the best, it's also completely forgettable. In article <25773@rochester.ARPA> ken@rochester.ARPA (SKY) writes: >That is what logic would lead one to expect and I agree with the >reasoning behind this conclusion. However, my experience has been that >running a new tape through the drive once, recording dummy data, makes it >more amenable to recording the second time. I know, it doesn't make sense. It makes sense if you change the base assumptions: That new tape has been sitting in a warehouse for months, and has been subjected to fairly large mechanical shocks (have you ever watched truck loader at their task?). Some of the oxide has been loosened. The first run through the tape drive `scrapes off' this extra oxide. (Try cleaning your tape heads immediately before, and again after, running a new tape.) This `oxide fluff' alters the recording properties of the drive. The second pass (after you have cleaned the drive) is therefore more reliable. A third set of assumptions: The tape was wound under a different tension than your drive generates. This means that the first run through your drive changes the `stretch' on the tape, loosening some of the surface oxide. The second run through the tape drive `scrapes off' this extra oxide, and so forth. Another: Make up your own! It is easy and fun. Cheap thrills! But now you have to test your hypotheses. Step 1: find a fresh tape.... -- In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690) UUCP: seismo!mimsy!chris ARPA/CSNet: chris@mimsy.umd.edu