Re: Adding disks with raid to existing raid system.

[Michael Evans <mjevans1983@gmail.com>]

On Mon, Mar 15, 2010 at 7:53 PM, Simon Matthews
<simon.d.matthews@gmail.com> wrote:
> On Mon, Mar 15, 2010 at 5:36 PM, Michael Evans <mjevans1983@gmail.com> wrote:
>> On Sun, Mar 14, 2010 at 10:23 PM, Simon Matthews
>> <simon.d.matthews@gmail.com> wrote:
>>> I have just built a system and have it booting off a software raid
>>> partition. The raid sets use devices /dev/md0, /dev/hd1, /dev/md2,
>>> /dev/md3.
>>>
>>> I now need to transfer some additional disks to this system. These
>>> disks are presently in another system where they host a number of raid
>>> sets, currently also /dev/md0 - /dev/md4.
>>>
>>> I need to ensure that the data on the raid set that I am adding to the
>>> system is not lost. However, clearly, I can't have the raid sets on
>>> these disks come up as /dev/md0-md4. How do I ensure this and have
>>> these raid sets come up on /dev/md5 and higher?
>>>
>>> Simon
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>>
>> Either use an mdadm.conf to specify the mapping of UUID to md device
>> (which will over-ride any auto-detected requests), or use the
>> home-host fallback.  Obviously the administrator specifying how they'd
>> prefer mdadm to assemble the drives is preferable.
>
> I'm not aware of the "home-host fallback" can you give me some pointers on this?
>>
>> You will probably want to regenerate your initrd; if you are using
>> auto-assembly on root without an initrd, I highly suggest upgrading to
>> use an initrd/initramfs.  You might find this one easy to customize
>> for your needs if your distribution lacks one or you dislike the one
>> it generates: http://sourceforge.net/projects/aeuio/
>
> Fortunately Gentoo includes mkinitrd so I can try this if other
> methods don't work reliably.
>
> Simon
>
>>
>

man mdadm
/host

--homehost=

This will override any HOMEHOST setting in the config file and
provides the identity of the host which should be considered the home
for any arrays.

... etc

Before asking any further questions I highly suggest reading the
manual, completely, at least twice.
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