On Dec 22, 2006, at 09:50, Anton B. Rang wrote:
Phantom writes and/or misdirected reads/writes:
I haven't seen probabilities published on this; obviously the disk
vendors would claim zero, but we believe they're slightly
wrong. ;-) That said, 1 in 10^8 bits would mean we’d have an
error in every 12 megabytes written! That’s clearly far too low.
1 in 10^8 blocks would be an error in every 46 gigabytes written;
that is also clearly far too low. (At 1 GB/second that would be a
phantom write every minute.)
Jim Gray (a well-known and respected database expert, currently at
Microsoft) clams that the drive/controller combination will write
data to the wrong place on the drive at a rate of about one incident/
drive/year. In a 400-drive array (JBOD or RAID, doesn't matter),
that would be about once a day. This is a kind of error that (so
far, at least) can only be detected (and potentially corrected, given
redundancy) by ZFS.
--Ed
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