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I run a data center. Disk drives that are left running continuously
last between two and three years. Three years is about 36 months.
The odds of a disk failing in any given month are roughly one in 36. The odds of two different drives failing in the same month are roughly one in 36 squared, or 1 in about 1,300. The odds of three drives failing in the same month is 36 cubed or 1 in 46,656. The odds of seven different drives failing in the same month is 37 to the 7th power = 1 in 78,664,164,096.
Of course this is very simplified because disk failure modes are more at end-of-service-life rather than linearly spread over median life. So what if I am off by a factor of 4X? This crude calculation gets us into the same astronomical ballpark. You could insure against this event happening by buying lottery tickets.
--theBuckWheat
More @ Doug Ross
I deal with statistical analysis at work everyday. I was thinking something along these lines myself. Then I considered what reasonable doubt might mean. As long as the odds of seven drives failing at the same time is considerably smaller than reasonable doubt of say 1 in 10,000 or so, I think prosecution and guilt would be a fairly sure thing. Then prison.
ReplyDeleteThank you and I'll vote for that. :)
DeleteIt's been a while since I dealt seriously with probability calculations but I think the odds might be even slimmer than those expressed in the article. I'm guessing the universe of computers in the IRS is in the thousands. When you consider that not only did 7 hard drives supposedly fail at the same time but that they were 7 specific
ReplyDeletehard drives out of a large universe of possible hard drives the odds get astronomical.