Re: Write and verify correct data to read-failed sectors before degrading array?

On Thursday September 16, tim@buttersideup.com wrote:

Just thinking out loud here, but I wonder if the following change is 
possible or worth making to this code?  For a failed read, where the 
block is then successfully read from another drive, then attempt to 
write the correct data for this block to the device with the read 
failure (to try to see if the drive firmware thinks this sector is still 
usable, and if not then maybe it will reallocate the failed sector).  If 
this write succeeds, and can be verified, then don't mark the sector bad 
(maybe just complain with a printk)..

This would get around a lot of mirror failures that I see in 
operation..  In the past, I've had mirrors go bad with individual failed 
sectors in different locations on both drives, the array is then 
unusable (and the database server is dead, in my experience) unless you 
manually try to knit it back together with dd.

Yes.  Great idea.  Just as good as every other time it gets suggested :-)
Unfortunately no-one has presented any actual *code* yet, and I
haven't found/made/allocated time to do it.

   http://neilb.web.cse.unsw.edu.au/SoftRaid/01084418693

NeilBrown