From mboxrd@z Thu Jan  1 00:00:00 1970
From: NeilBrown <neilb@suse.de>
Subject: Re: [RFC] md raid resync counter
Date: Tue, 5 Nov 2013 16:12:55 +1100
Message-ID: <20131105161255.130a9c52@notabene.brown>
References: <5273A5BC.5060109@gmail.com>
	<20131102104808.47834bdc@notabene.brown>
	<52776852.3020309@gmail.com>
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To: Jack Wang <xjtuwjp@gmail.com>
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On Mon, 04 Nov 2013 10:26:42 +0100 Jack Wang <xjtuwjp@gmail.com> wrote:

> On 11/02/2013 12:48 AM, NeilBrown wrote:
> > On Fri, 01 Nov 2013 13:59:40 +0100 Jack Wang <xjtuwjp@gmail.com> wrote:
> >=20
> >> Hi Neil and all,
> >>
> >> Is there anyway to know:
> >>
> >> 1. How often does a raid start to resync?
> >=20
> > Look at your logs?
> >=20
> >> 2. How many bytes did it resync?
> >=20
> > Look at "mismatch_cnt" in sysfs (and multiply by 512).
> >=20
> > NeilBrown
> >=20
> >
> Thanks Neil,
>=20
> You're always very helpful :)
>=20
> About the second one. As I checked in my system kernel 3.4.51
>=20
> 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]
>       [=3D=3D>..................]  recovery =3D 10.7% (2562240/23762944)
> finish=3D7.5min speed=3D46565K/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
>=20
> cat /sys/block/md1/md/degraded
> 1
>  cat /sys/block/md1/md/mismatch_cnt
> 0
> # cat /sys/block/md1/md/sync_completed
> 8911488 / 47525888
>=20
> 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.


>=20
> Jack


NeilBrown

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