On Jan 22, 2013, at 3:55 AM, Roy Sigurd Karlsbakk [off-list ref] wrote:

quoted

Coming from the zfs world, I've heard a few talk about the chances of
"silent errors", meaning the checksum on the drives match, but the
data being bad because of matching checksum (aka collisions). Does
anyone in here know the relative chance of something like that
happening with the checksums of current harddisks? Is the 1:10^14 or
1:10^15 chances for a URE in regard to this, or is that when the drive
reports an error, or those two combined?

A follow-up here. I see drive manufacturers report the chance of an URE is 1:10^14 for desktop drives, 1:10^15 for 7k2RPM enterprise drives and 1:10^16 for 10k and 15k enterprise drives (or most do). I was under the impression that "nearline"  / 7k2 enterprise drives were the same thing as desktop drives, only with a slightly different firmware (TLER and friends => don't do anything as stupid as going into "deep recovery mode" like some desktop drives do).

Any idea if there's a real difference between the hardware on enterprise and desktop 7k2 drives? Is this 10-fold difference between error rates real, or is it just marketing?

SNIA has said there are differences in ECC between consumer SATA, nearline SATA, and enterprise SAS for some time. They also distinguish quite a few other differences that aren't ECC related, but they don't discuss error rates directly. And this is old information…

http://www.snia.org/sites/default/education/tutorials/2007/spring/storage/Desktop_Nearline_Deltas_by_Design.pdf

Chris Murphy--
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