Re: Raid5 read error correction log

On Saturday June 3, patrik@ucolick.org wrote:

Hey Neil,

It would sure be nice if the log contained any info about the error
correction that's been done rather than simply saying "read error
corrected", like which array chunk, device and sector was corrected. I'm
having a persistent pending sector on a drive, and when I do check or
repair, it says "read error corrected" many times, but I don't know
whether it's doing the same sector over and over or if there are just so
many of them...  I seem to remember reading something about this on the
list some time ago, is it already in the kernel? (I'm running 2.6.17-rc4
now).

Yes.... added to todo list:
   include sector/dev info in read-error-corrected messages

Btw, when it does correct a read error, I assume it also tries to read
it again to verify that the correction worked?

Yes.  It doesn't check that the read returns the correct data, but it
does check that a read succeeds.  However I'm not certain that the
read request will punch through any cache on the drive.  It could be
that the reads return data out of the cache without accessing data on
the surface of the disk....

NeilBrown