Re: Adding disks with raid to existing raid system.

On Mon, Mar 15, 2010 at 9:59 PM, Michael Evans [off-list ref] wrote:

On Mon, Mar 15, 2010 at 7:53 PM, Simon Matthews
[off-list ref] wrote:

quoted

On Mon, Mar 15, 2010 at 5:36 PM, Michael Evans [off-list ref] wrote:

quoted

On Sun, Mar 14, 2010 at 10:23 PM, Simon Matthews
[off-list ref] wrote:

quoted

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?

quoted

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

quoted

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.

In my defense, I did try to google this, but I looked for "home-host"
or "home host" and nothing turned up. Many thanks for your help. I
think this will solve my question about added existing arrays to a
system.

Simon
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