On Mon Oct 06, 2014 at 03:39:12PM +0200, Patrik Horník wrote:
> 2014-10-06 15:36 GMT+02:00 Robin Hill <robin@xxxxxxxxxxxxxxx>:
> > On Mon Oct 06, 2014 at 03:29:13PM +0200, Patrik Horník wrote:
> >
> >> Hello,
> >>
> >> is it possible to cancel RAID 6 array check? echo check >
> >> /sys/block/mdX/md/sync_action apparently only pauses it and next check
> >> continuing from saved position. (I guess /sys/block/mdX/md/sync_min)
> >>
> >> I want to achieve two things:
> >>
> >> - Start check from the start of the array.
> >>
> >> - Be sure I can shutdown array without any ill effect because check
> >> was interrupted.
> >>
> >> I guess that position will be cleared when array is stopped and
> >> started again, but I dont want to guess and experiment... :)
> >>
> >
> > You'd echo idle to the sync_action to pause/stop the check. If you want
> > to restart from the beginning next time, just echo 0 to sync_min
> > (similarly, if you just want to check/repair a specific range then set
> > sync_min and sync_max before the check/repair).
> >
> OK, thanks. So that should be fully working and correct way to do it
> and I cant harm my array by this in any way?
>
A check is always safe (well, excepting physical disk issues or issues
with overloading the I/O subsystem, but those are issues not limited to
check) as it's read-only.
The sync_min and sync_max values need to be multiples of the chunk size
(it throws an error otherwise), which ensures a whole stripe is being
checked/repaired (otherwise you could have issues).
The kernel documentation describes setting sync_min/sync_max, so it's an
expected operation. Whether there's another way of doing the same thing
I don't know - I've not heard of one though.
Cheers,
Robin
--
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