[CentOS] raid on large disks?

Wed Oct 12 16:37:01 UTC 2011
David C. Miller <millerdc at fusion.gat.com>

----- Original Message -----
> From: "Les Mikesell" <lesmikesell at gmail.com>
> To: "CentOS mailing list" <centos at centos.org>
> Sent: Wednesday, October 12, 2011 9:28:48 AM
> Subject: Re: [CentOS] raid on large disks?
> On Wed, Oct 12, 2011 at 11:22 AM, David Miller <david3d at gmail.com>
> wrote:
> >>>
> >> With GPT that's set using flags.  This is done in parted with the
> >> command
> >> "set <partition number> raid on"
> >>
> >
> > I just thought of one other thing.  You'll want to read up on bios
> > boot if
> > these large drives are being used for the grub boot loader.
> >
> Not booting from them, but is there a problem with kernel
> autoassembly
> on large partitions?  I see this in dmsg:
> md: Autodetecting RAID arrays.
> md: invalid raid superblock magic on sde1
> md: sde1 has invalid sb, not importing!
> But
> mdadm --assemble /dev/md5 /dev/sde1
> works fine after booting.  (The array was created with a missing
> member which hasn't been added yet).

When using mdadm you don't even have to partition a drive if you are using the whole thing. Just make sure the block device is set to GPT in parted if it is not already. After creating the RAID1 get the uuid of the raid by doing mdadm -D /dev/dm5. Then use the following format in the /etc/mdadm.conf to have it auto assemble at boot.

ARRAY /dev/md5 devices=/dev/sd[e-f] uuid=$UUID_FROM_MDADM

David C Miller.