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The 2006 Linux File Systems Workshop
The 2006 Linux File Systems Workshop
Posted Jul 6, 2006 14:06 UTC (Thu) by nix (subscriber, #2304)In reply to: The 2006 Linux File Systems Workshop by hmh
Parent article: The 2006 Linux File Systems Workshop
md-raid can already do this.
Just stick in cron something like
2 5 15 * * echo check > /sys/block/md-$blah/md/sync_action
to check parity on array md-${blah} (which of course reads every block on every disk in the array).
(OK, so you might want something a bit more elaborate to prevent checking if sync_action for the array is not 'idle' so as not to interrupt a real resync.)
This will proceed in the background and respect other accesses to the block device by slowing down, just like md resyncs always have.
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The 2006 Linux File Systems Workshop
Posted Jul 6, 2006 14:29 UTC (Thu) by hmh (subscriber, #3838) [Link]
Thanks! That does half the job already, and will at least find errors that have already happened and attempt to fix them.
It would be nice to have a "scrub" action that actually writes the entire array (all member devices, all sectors) to refresh aged sectors, though. "check" won't help there, and forcing a resync on every member device in turn is a very awkward (not to mention suboptimal) way to do it.
The 2006 Linux File Systems Workshop
Posted Jul 6, 2006 15:23 UTC (Thu) by nix (subscriber, #2304) [Link]
Forcing a resync won't rewrite everything, in any case, only the parity stripes: the non-parity stripes will only be read (unless you hit a write error in the parity stripe, of course).
The 2006 Linux File Systems Workshop
Posted Jul 6, 2006 15:54 UTC (Thu) by hmh (subscriber, #3838) [Link]
You have to set the member device to be "refreshed" to faulty, hot-remove and hot-add it back. This is, of course, dangerous depending on your array configuration.
As I said, it is very awkward, and thus a scrub function would be welcome.