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Old 02-17-2009, 03:47 PM
Hendrik Boom
 
Default Yet another RAID admin question

I have successfully identified and decommissioned a failing RAID
partition -- my RAID1 was then running properly with only one of its two
twinned partitions. Every timr I booted, I got a message complaining
that it was deficient. The drive with the failing partition was indeed
defective, and has been physically removed from the computer. and
replaced with two new ones, which have been tested by exhaustive read-
write testing.

I've created partitions for the RAID on the new drivew, and successfully
added them.

The new drives are three times as big as the old ones. I'd like to drop
the remaining old one from the RAID setup now, so I can triple the size
of the RAID.

Now presumably I can use mdadm to software-fail it, or to remove it, or
something like that.

But I understand these partitions are marked in some way to identify them
as RAID members, and that these marks are used at boot time to asssemble
the RAID.

What do I have to do to make sure that after I have removed the old
member it is never again recognised as a RAID member?

-- hendrik


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Old 02-17-2009, 04:22 PM
martin f krafft
 
Default Yet another RAID admin question

also sprach Hendrik Boom <hendrik@topoi.pooq.com> [2009.02.17.1747 +0100]:
> But I understand these partitions are marked in some way to
> identify them as RAID members, and that these marks are used at
> boot time to asssemble the RAID.
>
> What do I have to do to make sure that after I have removed the
> old member it is never again recognised as a RAID member?

There's a superblock. When mdadm starts, it scans the devices
listed for DEVICES in mdadm.conf (or all partitions if it says
'partitions') for superblocks.

You can remove a superblock with --zero-superblock. See mdadm(8).

--
.'`. martin f. krafft <madduck@d.o> Related projects:
: :' : proud Debian developer http://debiansystem.info
`. `'` http://people.debian.org/~madduck http://vcs-pkg.org
`- Debian - when you have better things to do than fixing systems

a c programmer asked whether computers have buddha's nature.
as the answer, the master did "rm -rf" on the programmer's home
directory. and then the c programmer became enlightened...
 
Old 02-18-2009, 04:31 PM
Hendrik Boom
 
Default Yet another RAID admin question

On Tue, 17 Feb 2009 18:22:43 +0100, martin f krafft wrote:

> also sprach Hendrik Boom <hendrik@topoi.pooq.com> [2009.02.17.1747
> +0100]:
>> But I understand these partitions are marked in some way to identify
>> them as RAID members, and that these marks are used at boot time to
>> asssemble the RAID.
>>
>> What do I have to do to make sure that after I have removed the old
>> member it is never again recognised as a RAID member?
>
> There's a superblock. When mdadm starts, it scans the devices listed for
> DEVICES in mdadm.conf (or all partitions if it says 'partitions') for
> superblocks.
>
> You can remove a superblock with --zero-superblock. See mdadm(8).

So the procedure would be somehtinglike:

mdadm --fail /dev/md0 /dev/hda3
to stop it from using /dev/hda3. After this it should spend a happy hour
copying the data on /dev/sda3, the other active drive to /dev/sdb3. the
current spare.

mdadm --remove /dev/md0 /dev/hda3
to remove it from the set, and

mdadm --zero-superblock /dev/hda3
to make sure it never comes back. Presumably I'm not supposed to
mention /dev/md0 on this command because /dev/hda3 is no longer part of
it.

-- hendrik




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