The Probability of Hard Drive Faliure

[LostDutchman]

The odds of winning the  Florida  lottery are 1 in 22,957,480.

The odds of winning the Powerball is 1 in 175,223,510.

The odds of winning Mega Millions is 1 in 258,890,850.

The odds of a disk drive 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 (like what happened at the IRS when they received a letter asking about emails targeting conservative and pro Israeli groups) is 37 to the 7th power = 1 in 78,664,164,096. (that's over 78 Billion) In other words, the odds are greater that you will win the Florida Lottery 342 times than having those seven IRS hard drives crashing in the same month.



Gotcha!

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[bluefirecorp]

Not quite. Backblaze has THOUSANDS of HDDs running 24/7. They literally have a full time guy running around replacing disks.

Also, if disk were all bought at the same time, their MTBF is very close. Assuming it was a RAID5 / RAID6, rebuild on a RAID literally rapes disks and raises the chances of failing even more.


Here's some GREAT data on drive failures from backblaze: http://blog.backblaze.com/2014/01/21/what-hard-drive-should-i-buy/


Edit: More data: http://blog.backblaze.com/2013/11/12/how-long-do-disk-drives-last/

[LostDutchman]

Not quite. Backblaze has THOUSANDS of HDDs running 24/7. They literally have a full time guy running around replacing disks.

Also, if disk were all bought at the same time, their MTBF is very close. Assuming it was a RAID5 / RAID6, rebuild on a RAID literally rapes disks and raises the chances of failing even more.


Here's some GREAT data on drive failures from backblaze: http://blog.backblaze.com/2014/01/21/what-hard-drive-should-i-buy/

Uh, the post was a joke.

[ALToids]

I think Dutch was trying to point out utterly stupid it was for them to use the arguement that the hard drive crashed.  That's like saying my dog ate my homework.

Considering the IRS probably has a little more resources than the average citizen and with their servers with redundant RAID the chances of those selective emails be lost is like the chances of bruteforcing a Bitcoin private key.

[bluefirecorp]

I think Dutch was trying to point out utterly stupid it was for them to use the arguement that the hard drive crashed.  That's like saying my dog ate my homework.

Considering the IRS probably has a little more resources than the average citizen and with their servers with redundant RAID the chances of those selective emails be lost is like the chances of bruteforcing a Bitcoin private key.

Sadly, after seeing IT for local government and even state governments, it's a pretty valid excuse.

[LostDutchman]

I think Dutch was trying to point out utterly stupid it was for them to use the arguement that the hard drive crashed.  That's like saying my dog ate my homework.

Considering the IRS probably has a little more resources than the average citizen and with their servers with redundant RAID the chances of those selective emails be lost is like the chances of bruteforcing a Bitcoin private key.

Yeah!

Thanks for your kind and insightful post!