Matthew Dillon wrote:
Try that first. If it helps then it is a known issue. Basically
a combination of the on-disk write cache and possible ECC corrections,
remappings, or excessive remapped sectors can cause the drive to take
much longer then normal to complete a request. The default 5-second
timeout is insufficient.
From Western Digital's line of "enterprise" drives:
"RAID-specific time-limited error recovery (TLER) - Pioneered by WD,
this feature prevents drive fallout caused by the extended hard drive
error-recovery processes common to desktop drives."
Western Digital's information sheet on TLER states that they found most
RAID controllers will wait 8 seconds for a disk to respond before
dropping it from the RAID set. Consequently they changed their
"enterprise" drives to try reading a bad sector for only 7 seconds
before returning an error.
Therefore I think the FreeBSD timeout should also be set to 8 seconds
instead of 5 seconds. Desktop-targetted drives will not respond for
over 10 seconds, up to minutes, so its not worth setting the FreeBSD
timeout any higher.
More info:
http://www.wdc.com/en/library/sata/2579-001098.pdf
http://en.wikipedia.org/wiki/Time-Limited_Error_Recovery
- Andrew
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