Tuesday, January 09, 2007


Sometime in the late 80's I was working with dasd recovery software for a computing system that was in the process of being built, and we had an installation in the lab that had a terabyte (trillion) bytes of storage. We joked about it being "a terror byte", since if some of your software took that machine down, there was some degree of scrutiny since it took many hours to get it back up from a crash.

As luck would have it, part of the code I had produced re-allocated bad sectors on a drive, and it had to be "absolutely fail safe". I attempted to accomplish this by having a "save area" on the drive itself so that if anything went wrong during the recovery (power failure, other hardware or software failure), the proper state was always written out on the drive and when they attempted to bring the system up again, the sector reallocation process would complete as part of that process.

Unfortunately, I made an error in part of the code, so if certain events happened my recovery code would take and exception in a very restricted state of the machine on the way up, the boot would not complete, and the machine would never come back up again. Suddenly, I was in very high demand. Under a good deal of stress I managed to figure out what the problem was, make a patch to the machine and "wala", the monster trundled on through it's boot process to eventual completion and my "programmer humility" went up a bit. Part of the magic of being an operating system programmer is that when you screw up it takes the whole machine down. At that point, I was one of those special operating system programmers that if I made a mistake, your machine would never boot again ... unless you completely re-installed it from scratch and lost all your data. "Power" ... but with stress.

So what makes me think of this? Well, the machine I am typing this in on sitting on my desk officially has 1.1 terabyte of storage! I heard a lot of conflicting stories about how much the lab machine I crashed was worth, but it was certainly "millions". The grand total for the cost on this? Something around $400, and that is only because one of the 320GB drives is last years model and I think I paid $150 for it. There is another $99 320GB EIDE drives in there and two 250GB SATA drives that I picked up for under $80 each. Things really do change in twenty years. From a room full of drives worth millions to a machine under my desk worth "hundreds"!

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