Re: md raid behavior, bad sector uncorrectable read error

On 08/19/12 11:47, Mikael Abrahamsson wrote:

On Sat, 18 Aug 2012, Chris Murphy wrote:

quoted

If the affected chunk is rebuilt from parity (or copy in case of
mirror), does md raid issue a write command to write the rebuilt chunk
back to the disk at the same LBAs? If so, shouldn't this force the
drive to determine if the sector error is transient or persistent, and
if persistent the disk firmware will remap the bad sector to a reserve
sector?

If I remember correctly from what has been described here before, a read
error will cause a re-write with information created from parity, and
the drive should figure it out (either is successfully writes the new
information to the existing sector, or if it can't, it writes it to a
spare sector (re-map)). If it throws a write error, the drive is kicked
from the array (because a drive with write errors is clearly defective).

So yes, you're correct in your assumption from what I know.

Also, SMARTd would throw up errors when monitoring such drive when a re-map occurs, mdadm may not even notice this if the remap happens successfully.