recovering a mirrored arry.

recovering a mirrored arry.

[Keld Simonsen]

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 tat actually one of the copies were correct.
So I would like to try out the consistency of each part of the raid10
(it is 2-partition arrys, and then if I find one that is consisten 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 oter 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

Re: recovering a mirrored arry.

[Keld Simonsen]

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

Re: recovering a mirrored arry.

[Kristleifur Daðason]

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
> the body of a message to majordomo@vger.kernel.org
> 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".

Hope this helps!
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Re: recovering a mirrored arry.

[Keld Simonsen]

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
> > the body of a message to majordomo@vger.kernel.org
> > 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
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Re: recovering a mirrored arry.

[Kristleifur Daðason]

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
>> > the body of a message to majordomo@vger.kernel.org
>> > 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?
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Re: recovering a mirrored arry.

[Keld Simonsen]

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
> >> > the body of a message to majordomo@vger.kernel.org
> >> > 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
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Re: recovering a mirrored arry.

[Kristleifur Daðason]

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
>> >> > the body of a message to majordomo@vger.kernel.org
>> >> > 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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RE: recovering a mirrored arry.

[Guy Watkins]

} 
} I tried missing, but mdadm said that it could not find missing as a
} device,
} for assemble mode.
} 
} best regards
} keld

I bet it would help a lot if you showed your command line.

You might be doing something silly like /dev/missing and we don't know it.

:)

Re: recovering a mirrored arry.

[Robin Hill]

[-- Attachment #1: Type: text/plain, Size: 3204 bytes --]

On Fri Feb 05, 2010 at 07:50:44PM +0100, Keld Simonsen 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
> > > the body of a message to majordomo@vger.kernel.org
> > > 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.
> 
No, as the manual page says, "missing" is only used for creating an
array, not for assembling.

If you only give a single device in the assemble command then mdadm
_ought_ to only use that to assemble the array.  I'm not 100% sure that
it does it though - probably worth testing with loopback devices first.

The other option would be to use "create" to create new degraded arrays
containing only the single disks.  You'd need to make sure you used the
same settings as for the old array though.

Alternately, physically disconnect the drives in turn and assemble the
array with the single drive.

Cheers,
    Robin
-- 
     ___        
    ( ' }     |       Robin Hill        <robin@robinhill.me.uk> |
   / / )      | Little Jim says ....                            |
  // !!       |      "He fallen in de water !!"                 |

[-- Attachment #2: Type: application/pgp-signature, Size: 198 bytes --]

Re: recovering a mirrored arry.

[Keld Simonsen]

On Fri, Feb 05, 2010 at 10:42:25PM +0000, Robin Hill wrote:
> On Fri Feb 05, 2010 at 07:50:44PM +0100, Keld Simonsen 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
> > > > the body of a message to majordomo@vger.kernel.org
> > > > 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.
> > 
> No, as the manual page says, "missing" is only used for creating an
> array, not for assembling.
> 
> If you only give a single device in the assemble command then mdadm
> _ought_ to only use that to assemble the array.  I'm not 100% sure that
> it does it though - probably worth testing with loopback devices first.
> 
> The other option would be to use "create" to create new degraded arrays
> containing only the single disks.  You'd need to make sure you used the
> same settings as for the old array though.
> 
> Alternately, physically disconnect the drives in turn and assemble the
> array with the single drive.
> 
> Cheers,
>     Robin
> -- 
>      ___        
>     ( ' }     |       Robin Hill        <robin@robinhill.me.uk> |
>    / / )      | Little Jim says ....                            |
>   // !!       |      "He fallen in de water !!"                 |


I tried a number of ways to trick mdadm to assemble the raid with only
one partition. It seems like mdadm -A neither accepts a "missing"
argument nor just a single device. But the following worked.

I changed the "DEVICES" entry in mdadm.conf . to not list the device
that I wanted to exclude. I could then assemble and fsck each of the
parts of the mirrored array (changing mdadm DEVICES to exclude the
appropiate device).

And with good result! One of the devices were badly damaged, while the
other was intact! So long, so good.

Is this sufficiently interesting to warrant an entry on the wiki?

Best regards
keld

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