Wednesday, September 26, 2007

I, of course, are prefect

InfoWorld's "Off the Record" posed an interesting question. First the background. Years ago, a network administrator was running into strange problems with tape backups. Several problems were ruled out, including the integrity of the tapes themselves, daylight savings time, and so forth. It turns out the problem was caused by things which most people consider admirable - saving money and going green:

When we first set up the 8mm backup procedures, I carefully typed the tape IDs on the supplied labels ("Monday," "Tuesday," "Week 1," and so on) to make everything all nice and professional looking. When I retired a tape to replace it with a new one, I would peel the label off the old one and stick it on the new one, to avoid having to type new labels. As time went by, the sticky on the back of the labels would get less sticky during a transfer, and I would supplement it with a little clear cellophane tape to hold the label on securely.

Sounds like a good idea, right? Re-use labels; why waste them? They can't affect the tape, can they? Ah, but they can:

The bottom side of any kind of tape cartridge has several holes, many of them there to mate with pins in the deck to ensure proper alignment. Others are there to tell the deck about specific characteristics of the tape cartridge. One of these holes is there to tell the deck that it is a high capacity tape. A little corner of the cellophane tape that held on my label was covering this hole, making the deck think the tape had only half the capacity it actually had. So it stopped writing to the tape when it reached this amount of data, and dutifully asked for another one. I had innocently transferred this same tape and label piece to each tape as I replaced it, ensuring that I transferred the problem to each new tape. It wasn't much, but it was just enough. When I cut off the little tag of cellophane tape that had been covering the hole, my Monday problem went away.

OK, so that's the problem and the solution. Here's the interesting question:

I returned to the VAX/VMS board to update everyone on my solution. There wasn't much response, but one I found disturbing. "Wow, I'm really surprised you admitted to doing such a dumb thing!" Well, my ego isn't so sensitive that I can't admit to brain freezes, so I was puzzled by his anti-candor attitude. But my question to him, and to you, is: Would you have figured it out sooner?

For the record, here's my response:

I probably wouldn't have caught it - when you check the integrity of the tape, you don't think to check the label.

It might have been easier to diagnose if the problem occurred midweek, but having the problem occur on Monday suggested too many false solutions to the problem.

Another response was slightly different:

I wouldn't have had to figure it out, because I would never had this problem, for a couple of reasons:

1. I know better than to cover holes on a tape cartridge.

2. I'm not so cheap that I re-use tape labels. Last time I checked, each and every new tape comes with a new set of labels. Even in the day of 8mm tapes this was true.

Even if someone working for me had made this mistake, it wouldn't have taken a year to figure it out. It took you a year before you thought to look at the tape cartridge?

Maybe this article should be titled "Label Me Moron."

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