Robin Hill wrote:
On Mon Jan 11, 2010 at 11:00:40AM -0700, Tim Bock wrote:
Hello,
Excluding the obvious multi-disk or bus failures, can anyone describe
what type of disk failure a raid cannot detect/recover from?
I have had two disk failures over the last three months, and in spite of
having a hot spare, manual intervention was required each time to make
the raid usable again. I'm just not sure if I'm not setting something
up right, or if there is some other issue.
Thanks for any comments or suggestions.
Any failure where the disk doesn't actually return an error (within a
reasonable time). For example, consumer grade disks often have very
long retry times - this can mean the array in unusable for a long time
until the disk eventually fails the read.
If the disk actually returns an error then, AFAIK, the RAID array should
always be able to recover from it.
The problem is that the admin should be able to set a timeout after
which recovery takes place even if the drive hasn't returned a bad
status. And some form of counter could be kept such that after a number
of these the drive is failed. There is no solution, Neil says the
timeout should be in the driver, the driver writers say that if it hurts
md the timeout should be there. Everyone points the finger at some other
code and says "there."
This is not lazyness or buck passing, Neil feels that md is not the
place, but putting it elsewhere causes other problems. Until someone
says "perfect is the enemy of good enough" and puts a timer where it
will solve the problem, this behavior will continue.
--
Bill Davidsen <davidsen@xxxxxxx>
"We can't solve today's problems by using the same thinking we
used in creating them." - Einstein
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
