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Re: Replacing failed drive in software RAID



Veljko wrote:
> Veljko wrote:
> > I replaced sdd drive and that went without problem, but after
> > replacing sda, the drive with boot partition and MBR, system
> > stalled at "veryfying dmi pool data". So I inserted debian CD and
> > went with rescue mode. I haven't used it so I have some questions.
> > 
> > I'm offered to reassemble RAID. Is it safe to use auto reconfigure
> > option or should I assemble all three manually?

As long as all of the disks are to be assembled then automatic mode
should be okay.  Don't use automatic mode if you have disks attached
that you do not want to be assembled.  The automated mode will scan to
see what is there and assemble anything that it can assemble.  But if
the only disks attached are the ones you want to assemble then I think
the automated mode is okay.

If the rescue tries to assemble two arrays that both have the same
minor number then it will assign a new minor number to one of the
arrays.  This really isn't bad but causes the renumbered ones to be in
the wrong place.  This can be corrected using the --update=super-minor
option.  This shouldn't be needed but I will mention it just in case.

> > If I should go with manually, what to do with md0? It's RAID1 for boot
> > partition and now there is only one drive.

You can only start it in degraded mode with one disk.  One disk is
enough to start the array.

> > Should I recreate md1 and md2 with three drives? Would that work?

You have lost me on the context of this question.

> > After this is done successfully, I assume I should go with:
> > # vgscan
> > # vgchange -a y volume_group_name

That should not be needed.  LVM happens at the next layer up.  LVM
shouldn't ever notice that the physical volume has gone away.  There
shouldn't be any need to make any LVM changes at all.

Unless you are doing something that you haven't explained.  :-/

In rescue mode simply assemble the raid.  Then it will ask you to
select a root file system.  If you are using lvm and have named them
appropriately then this should be easy.  I always name my root "root"
so that I can find it easily.

> > and mount manually all partitions (there is root and swap, so I
> > guess I only need to mount root). Am I right?

The installer will ask you for your root partition.  Then it will
offer you a shell in the target environment.  After getting a shell in
the root partition you will need to mount the other partitions.

  # mount -a

> > Then, after creating partition table and adding new drive into
> > RAID, would simple:
> > # grub-install /dev/sda
> > do the job?

Yes.

> > Anything else to think about?
> 
> Can anyone just confirm that it is safe to use auto reassemble RAID feature
> from Debian installer?

It has always worked for me.  As long as all of the attached disks are
to be assembled.  Don't do the automated if you have extra disks that
should not be assembled.

Bob

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