Re: recovering a mirrored arry.

["Kristleifur Daðason" <kristleifur@gmail.com>]

On Fri, Feb 5, 2010 at 10:38 PM, Keld Simonsen <keld@keldix.com> wrote:
> On Fri, Feb 05, 2010 at 10:06:38PM +0000, Kristleifur Daðason wrote:
>> On Fri, Feb 5, 2010 at 6:50 PM, Keld Simonsen <keld@keldix.com> wrote:
>> > On Fri, Feb 05, 2010 at 04:25:02PM +0000, Kristleifur Daðason wrote:
>> >> On Fri, Feb 5, 2010 at 1:19 AM, Keld Simonsen <keld@keldix.com> wrote:
>> >> > On Wed, Feb 03, 2010 at 03:57:58AM +0100, Keld Simonsen wrote:
>> >> > Hi
>> >> >
>> >> >
>> >> > can anybody help me with this? I am stuck with recovering my system here.
>> >> > is it a sensible thing ro do?
>> >> >
>> >> > best regards
>> >> > keld
>> >> >
>> >> >> Hi
>> >> >>
>> >> >> I got 2 arrays in error of the raid10 type.
>> >> >>
>> >> >> I think this is because my motherboard died, and then the fs were
>> >> >> corrupted.
>> >> >>
>> >> >> My thoughts were that actually one of the copies could be correct.
>> >> >> So I would like to try out the consistency of each part of the raid10
>> >> >> (it is 2-partition arrays), and then if I find one that is consistent, then
>> >> >> resync the faulty one with the good one.
>> >> >>
>> >> >> How do I do this?
>> >> >>
>> >> >> it seems that I cannot just assemble an array with a missing part.
>> >> >> If I assemble the full array, is there then a risk of the bad one
>> >> >> corrupting the good one? And can I declare one of the disks faulty
>> >> >> then test the other one, then declare nbr 2 disk for faulty and
>> >> >> declare the first one as good?
>> >> >>
>> >> >> I dont see anything on the wiki on this.
>> >> >>
>> >> >> best regards
>> >> >> keld
>> >> > --
>> >> > To unsubscribe from this list: send the line "unsubscribe linux-raid" in
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>> >> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
>> >> >
>> >>
>> >>
>> >> I wish I could help more, but check out this from the mdadm man page:
>> >>
>> >>        To create a "degraded" array in which some devices are missing,
>> >> simply give
>> >>        the word "missing" in place of a device name.  This  will
>> >> cause  mdadm  to
>> >>        leave  the  corresponding  slot  in  the array empty.  For a
>> >> RAID4 or RAID5
>> >>        array at most one slot can be "missing"; for a  RAID6  array
>> >> at  most  two
>> >>        slots.   For a RAID1 array, only one real device needs to be
>> >> given.  All of
>> >>        the others can be "missing".
>> >
>> > I tried missing, but mdadm said that it could not find missing as a device,
>> > for assemble mode.
>> >
>> > best regards
>> > keld
>> >
>>
>> Hmmm ... I guess your version of mdadm may be too old. Which version
>> do you have?
>
> v2.5.3
>
> best regards
> keld
>

Well, that's at least kind of old ... might be worth a build. Luckily,
mdadm is pretty simple to compile.

As a heuristic: Does your "man mdadm" page state that you can use the
'missing' option? If it does, well, your mdadm ought to support it too
...
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