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Date: Thu, 27 Nov 2014 13:52:19 +0100
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Subject: Re: [linux-lvm] LVM RAID1 syncing component
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With DM/LVM it is always the last images added when converting (to)
raid1; see "lvs -a".

If you for instance convert from linear to raid1 with "lvconvert -m1 
--type raid1  $LV",
the second (and last) device named /dev/$VG/${LV}_rimage_1 will be 
resynchronized
from the first /dev/$VG/${LV}_rimage_0 (i.e. the former linear device).

As mentioned below, the copy_percent aka sync_percent tells you how far 
the sync process got
unless 100% when it's finished.

-- lvmguy


On 11/26/2014 02:20 PM, Joe Lawrence wrote:
> On Tue, 25 Nov 2014 22:42:38 -0700
> Chris Murphy <lists@colorremedies.com> wrote:
>
>> On Mon, Nov 24, 2014 at 9:07 PM, Joe Lawrence <joe.lawrence@stratus.com> wrote:
>>> Does anyone know how its possible to determine which side of an LVM RAID 1
>>> is the stale partner during RAID resync?
>>>
>>> In ordinary MD RAID, I believe you can check
>>> /sys/block/md0/md/dev-XXX/state, but LVM RAID seems to hide those files
>>> when leveraging the MD code.  I've looked though pvs/vgs/lvs manpages, but
>>> can't figure anything out there either.
>> Rather indirectly: iotop which will show you which devices are mostly
>> being read from and written to.
>>
>> # lvs -a -o copy_percent
>> Anything less than 100% is syncing. I think.
>>
> >From the manpages I see the following attribute bits:
>
> * lvs, lv_attr bit Volume Health: (p)artial
> * vgs, vg_attr bit (p)artial: one or more physical volumes belonging
>         to the volume group are missing from the system
> * pvs, pv_attr bit (m)issing
>
> along with the lvs copy_percent (is this similar to sync_percent) that
> you mentioned.  That's about it.
>
> Since there seems to be no real underlying MD device, I'm assuming that
> ioctls are out of the question as well.
>
> -- Joe
>
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