Am 29.06.2017 um 12:14 schrieb Gandalf Corvotempesta:
2017-06-29 12:10 GMT+02:00 Reindl Harald <h.reindl@xxxxxxxxxxxxx>:
there is nothing like "unused part of the array" since the linux-raid-layer
knows nothing about the filesystem on top and hence a raid-check (scrub)
reads every block as said hardware controller
Yes, this during a scrub.
Without a scrub, kernel know nothing about an unused part of the array.
Let's assume a unreadable sector is found during a scrub. What
happens? mdadm kick-out the disk from the array? It tried to
reallocate the failed sector somewhere keeping the disk up and running
(and thus, resolving the URE that would prevent a successful resync?)
it tries to re-write the data block (depending if repair is enabled)
normally the disk firmware itself is aware of that event and realloctes
a spare block so the rewrite just suceeds until the disk runs out of
spare sectors
but well, even if it just kicks out the disk soon enough you can replace
it, the array rebuilds and nothing happened - without smart-check/scrub
sooner or later it's detected due rebuild after a disk failed and the
array is gone
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