Tracy R Reed wrote: > Gus Wirth wrote: >> You also have to be careful when evaluating reliability. There are a >> lot of things that go into determining reliability figures. > > Speaking only of the reliablity of the hard drives themselves the Google > and CMU papers that came out this year about hard drive reliability were > very interesting. > >> Hard drive failures are only a small portion of the overall figure for >> reliability for a computer. In particular, even if your drives are >> mirrored you are only protected against a small subset of single drive >> failures where the failure mode is non-catastrophic to other parts of >> the system. If a drive fails by shorting the +12 to the +5 volt supply >> (this is highly unlikely) it could take just about everything else >> with it rendering the mirror useless. > > I have had many drives die but never had a short across the bus like > that. As you said, highly unlikely. And that sort of thing is what I > have backup copies for. Bacula to the rescue! > >> One of the biggest problems in determining reliability of anything is >> getting a history of the item. As I've mentioned before, all the MTBF >> (Mean Time Before Failure) you see on computer hardware are just >> guesses because the hardware product cycle is somewhere near 9 months, >> much shorter than the expected MTBF. So there isn't enough data >> collected to verify the estimates, and there is no economic incentive >> to do anything about it. > > The Google and CMU papers were the best research done so far. Brief > summary of the two: SCSI isn't any more reliable than IDE. Temperature > doesn't affect drives as much as we thought. Chances of a multiple drive > failure in a RAID 5 are higher than we think. They wouldn't tell us > which vendors were more reliable than others. >
Did they not also cast serious doubts on the traditional bathtub failure distribution? Regards, ..jim -- [email protected] http://www.kernel-panic.org/cgi-bin/mailman/listinfo/kplug-list
