> From: Brandon Allbery [mailto:allber...@gmail.com] > > And it prevents the head scribbling garbage during a power failure how? > (Yes, this kind of failure does happen.)
In tractor trailers, the brakes are spring loaded, forced into the fully locked, braking position. When the engine is running, the compressor builds up enough pressure to disengage the brakes, as operated by the driver's brake pedal. So in the absence of power, the brakes fail safe. (Those trucks are way too heavy for the driver to stop without power assistance.) 23 years ago on my 286, with a 20Mb MFM hard drive, I needed to issue the "park" instruction before shutting off the computer. C:\DOS\park.com This would position the head on a safe landing zone, so as not to crash on the drive and damage data. There was even a physical head lock mechanism, in case you need to transport the hard drive anywhere. In the early days of ATA, I was pleased to learn, that drive manufacturers universally incorporated spring loaded mechanisms, which would automatically suck the head away from the disk surface in the event of insufficient power, and automatically lock position just in case the drive would be transported. I would be extremely shocked, to learn that later manufacturers decided this feature was unnecessary, and actively decided it would be ok to allow random corruption to random disk sectors in the event of power loss. I stand by my assertion. The journal knows all the blocks that could possibly become corrupted by power outage or other crash. _______________________________________________ Tech mailing list Tech@lists.lopsa.org https://lists.lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
