Moved drives between machines... now, MIA.

Moved drives between machines... now, MIA.

[Ken D'Ambrosio]

Okay, so I swapped six drives from one machine to another.  I was very,
very careful to ensure that the drives were plugged in in the
corresponding order that they'd been plugged in in the first machine. 
Now, fdisk shows no partitions in two of my three mirrors.  This fills me
with a distinct lack of warmth and fuzziness.  /etc/mdadm/mdadm.conf
addresses the two (MIA) mirrors with /dev/sd[abef]1 designators, which
can, of course, get jumbled in a transition.  Any tips on how to go
forward would be gratefully appreciated -- I *really* don't want to have
to go to backups.

Thanks!

-Ken


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Re: Moved drives between machines... now, MIA.

[Ryan Wagoner]

On Fri, Jan 29, 2010 at 1:52 PM, Ken D'Ambrosio <ken@jots.org> wrote:
> Okay, so I swapped six drives from one machine to another.  I was very,
> very careful to ensure that the drives were plugged in in the
> corresponding order that they'd been plugged in in the first machine.
> Now, fdisk shows no partitions in two of my three mirrors.  This fills me
> with a distinct lack of warmth and fuzziness.  /etc/mdadm/mdadm.conf
> addresses the two (MIA) mirrors with /dev/sd[abef]1 designators, which
> can, of course, get jumbled in a transition.  Any tips on how to go
> forward would be gratefully appreciated -- I *really* don't want to have
> to go to backups.
>
> Thanks!
>
> -Ken
>
>
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You did make a new mdadm.conf with the correct devices for each array
right? If not try running and seeing if your arrays come up. If they
do then copy /tmp/mdadm.conf to /etc/mdadm/mdadm.conf

mdadm --examine --scan --config=partitions > /tmp/mdadm.conf
mdadm --assemble --scan --config=/tmp/mdadm.conf

Ryan
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Re: Moved drives between machines... now, MIA.

[Michael Evans]

1) look at your syslog / dmesg to see what auto-detection and initial
tries by your configuration said.
2) You probably want something like I keep as a backup in my
initrd/initramfs images:

/sbin/mdadm --examine --scan /dev/[sh]d* /dev/mapper/* >
/etc/mdadm.conf.OR.SOME.FILE
/sbin/mdadm --assemble --scan --no-degraded
--config=/etc/mdadm.conf.OR.SOME.FILE

If you drop the .OR.SOME.FILE you don't need to specify a non-default
config.  You also don't need to specify any config if you explicitly
name your devices: I'm asking mdadm to examine every block device (and
partition on such) that I think even possibly could be a raid member.

Re: Moved drives between machines... now, MIA.

[Ken D'Ambrosio]

> You did make a new mdadm.conf with the correct devices for each array
> right? If not try running and seeing if your arrays come up. If they do
> then copy /tmp/mdadm.conf to /etc/mdadm/mdadm.conf
>
> mdadm --examine --scan --config=partitions > /tmp/mdadm.conf mdadm
> --assemble --scan --config=/tmp/mdadm.conf

Hmmm.  I was hoping what I'd been doing had been "wrong" somehow, but what
you've got is pretty much what I did.  And here's the output (which
confuses the living Hell out of me):

ARRAY /dev/md0 level=raid1 num-devices=2
UUID=f2de81aa:ccd40fc9:01dc0b99:e8df86c1
ARRAY /dev/md1 level=raid1 num-devices=2
UUID=837925b3:f9f0e1b1:02f450c9:474613c9
ARRAY /dev/md1 level=raid1 num-devices=2
UUID=b6af942c:119cd1fc:02f450c9:474613c9

(Note how the second half of the last two UUIDs is the same, and the last
two UUIDs are both for /dev/md1.)

Guess it's time to go to the tapes, huh?

Thanks,

-Ken


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Re: Moved drives between machines... now, MIA.

[Jon Hardcastle]

--- On Tue, 2/2/10, Ken D'Ambrosio <ken@jots.org> wrote:

> From: Ken D'Ambrosio <ken@jots.org>
> Subject: Re: Moved drives between machines... now, MIA.
> To: "Ryan Wagoner" <rswagoner@gmail.com>
> Cc: linux-raid@vger.kernel.org
> Date: Tuesday, 2 February, 2010, 15:36
> > You did make a new mdadm.conf
> with the correct devices for each array
> > right? If not try running and seeing if your arrays
> come up. If they do
> > then copy /tmp/mdadm.conf to /etc/mdadm/mdadm.conf
> >
> > mdadm --examine --scan --config=partitions >
> /tmp/mdadm.conf mdadm
> > --assemble --scan --config=/tmp/mdadm.conf
> 
> Hmmm.  I was hoping what I'd been doing had been
> "wrong" somehow, but what
> you've got is pretty much what I did.  And here's the
> output (which
> confuses the living Hell out of me):
> 
> ARRAY /dev/md0 level=raid1 num-devices=2
> UUID=f2de81aa:ccd40fc9:01dc0b99:e8df86c1
> ARRAY /dev/md1 level=raid1 num-devices=2
> UUID=837925b3:f9f0e1b1:02f450c9:474613c9
> ARRAY /dev/md1 level=raid1 num-devices=2
> UUID=b6af942c:119cd1fc:02f450c9:474613c9
> 
> (Note how the second half of the last two UUIDs is the
> same, and the last
> two UUIDs are both for /dev/md1.)
> 
> Guess it's time to go to the tapes, huh?
> 
> Thanks,
> 
> -Ken
> 
> 

So basically all you have done is remove the drives from 1 machine and insert in another? I would really hope that, that would not trash data... I have never tried it mind. i did recently change my drive order though just unplugged and re-plugged in a completely new order.


      
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Re: Moved drives between machines... now, MIA.

[Neil Brown]

On Tue, 2 Feb 2010 08:35:23 -0800 (PST)
Jon Hardcastle <jd_hardcastle@yahoo.com> wrote:

> --- On Tue, 2/2/10, Ken D'Ambrosio <ken@jots.org> wrote:
> 
> > From: Ken D'Ambrosio <ken@jots.org>
> > Subject: Re: Moved drives between machines... now, MIA.
> > To: "Ryan Wagoner" <rswagoner@gmail.com>
> > Cc: linux-raid@vger.kernel.org
> > Date: Tuesday, 2 February, 2010, 15:36
> > > You did make a new mdadm.conf
> > with the correct devices for each array
> > > right? If not try running and seeing if your arrays
> > come up. If they do
> > > then copy /tmp/mdadm.conf to /etc/mdadm/mdadm.conf
> > >
> > > mdadm --examine --scan --config=partitions >
> > /tmp/mdadm.conf mdadm
> > > --assemble --scan --config=/tmp/mdadm.conf
> > 
> > Hmmm.  I was hoping what I'd been doing had been
> > "wrong" somehow, but what
> > you've got is pretty much what I did.  And here's the
> > output (which
> > confuses the living Hell out of me):
> > 
> > ARRAY /dev/md0 level=raid1 num-devices=2
> > UUID=f2de81aa:ccd40fc9:01dc0b99:e8df86c1
> > ARRAY /dev/md1 level=raid1 num-devices=2
> > UUID=837925b3:f9f0e1b1:02f450c9:474613c9
> > ARRAY /dev/md1 level=raid1 num-devices=2
> > UUID=b6af942c:119cd1fc:02f450c9:474613c9
> > 
> > (Note how the second half of the last two UUIDs is the
> > same, and the last
> > two UUIDs are both for /dev/md1.)
> > 
> > Guess it's time to go to the tapes, huh?
> > 
> > Thanks,
> > 
> > -Ken
> > 
> > 
> 
> So basically all you have done is remove the drives from 1 machine and insert in another? I would really hope that, that would not trash data... I have never tried it mind. i did recently change my drive order though just unplugged and re-plugged in a completely new order.
> 

No, that in itself would not cause a problem.
If you have two machines each with /dev/md1, and you move the devices from
one to the other, that other will appear to have two different  /dev/md1
which would be confusing.  mdadm tries to be careful and will only assemble
one of them, or will assemble them both with different names.

The commonality in the tail of the uuid of the two /dev/md1 array is simply
because they were created with the same HOMEHOST.

You can assemble the arrays manually with something like

 mdadm -As /dev/md1 --uuid=.......
 mdadm -As /dev/md1a --uuid=...there-other-one....

Then look at the contents.

NeilBrown

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Moved drives between machines... now, MIA.

[Ken D'Ambrosio]

[Apologies if this is a dup; sent the original before my subscription was
confirmed.]

Okay, so I swapped six drives from one machine to another.  I was very,
very careful to ensure that the drives were plugged in in the
corresponding order that they'd been plugged in in the first machine.
Now, fdisk shows no partitions in two of my three mirrors.  This fills me
with a distinct lack of warmth and fuzziness.  /etc/mdadm/mdadm.conf
addresses the two (MIA) mirrors with /dev/sd[abef]1 designators, which
can, of course, get jumbled in a transition.  Any tips on how to go
forward would be gratefully appreciated -- I *really* don't want to have
to go to backups.

Thanks!

-Ken



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