On Mon Oct 06, 2014 at 03:39:12PM +0200, Patrik Horník wrote:

2014-10-06 15:36 GMT+02:00 Robin Hill [off-list ref]:

quoted

On Mon Oct 06, 2014 at 03:29:13PM +0200, Patrik Horník wrote:

quoted

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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