On Mon, 04 Nov 2013 10:26:42 +0100 Jack Wang [off-list ref] wrote:

On 11/02/2013 12:48 AM, NeilBrown wrote:

quoted

On Fri, 01 Nov 2013 13:59:40 +0100 Jack Wang [off-list ref] wrote:

quoted

Hi Neil and all,

Is there anyway to know:

1. How often does a raid start to resync?

Look at your logs?

quoted

2. How many bytes did it resync?

Look at "mismatch_cnt" in sysfs (and multiply by 512).

NeilBrown

Thanks Neil,

You're always very helpful :)

About the second one. As I checked in my system kernel 3.4.51

when raid is resync:
cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 dm-1[3] dm-2[2]
      23762944 blocks super 1.2 [2/1] [_U]
      [==>..................]  recovery = 10.7% (2562240/23762944)
finish=7.5min speed=46565K/sec

This array is doing "recovery", not "resync".

"Resync" is when the devices should all contains the same data but maybe
don't due to some  error.  So md/raid1 checks and fixes the errors.
"recovery" is when a spare has been added and data is being copied  onto it.

# cat /sys/block/md1/md/mismatch_cnt
0

cat /sys/block/md1/md/degraded
1
 cat /sys/block/md1/md/mismatch_cnt
0
# cat /sys/block/md1/md/sync_completed
8911488 / 47525888

mismatch_cnt is 0, sync_completed look what I want?

"sync_completed" is a number which is somewhat smaller than the number of
sectors that have been be processed by the current
sync/repair/recover/whatever.

Slightly smaller because it is only updated occasionally.

I don't really know what you want because you didn't say what you would do
with the information, but it is possible that this is what you want.

Jack

NeilBrown