Configuring RAID 10 with RedHat ES 4 (64 bit)

[Andy Mountford]

Hi,

I am trying to configure an array of 12 disks in a RAID 10
configuration. All 12 disks are identical 146Gb drives.

First off, on each disk I created a single partition which spanned the
whole disk with a system id of 0xFD. After writing the partition
table, a print confirmed all looked good.

Secondly, I used mdadm to create 6 RAID 1 pairs. (mirrored). 

mdadm --create /dev/md0 --level=1 -n 2 /dev/sda /dev/sdb
mdadm --create /dev/md1 --level=1 -n 2 /dev/sdc /dev/sdd
mdadm --create /dev/md2 --level=1 -n 2 /dev/sde /dev/sdf
mdadm --create /dev/md3 --level=1 -n 2 /dev/sdg /dev/sdh
mdadm --create /dev/md4 --level=1 -n 2 /dev/sdi /dev/sdj
mdadm --create /dev/md5 --level=1 -n 2 /dev/sdk /dev/sdl

cat /proc/mdstat showed the devices syncing. Once this had completed I
created a final meta device which striped the RAID1 meta devices. e.g.

mdadm --create /dev/md6 --level 0 -n 6 /dev/md0 dev/md1 dev/md2
dev/md3 dev/md4 dev/md5

I could then create a filesystem on the new array and mount it - all
looked good. However, 2 things concerned me:

1. After creating the RAID array, the partition table for all the
disks involved was empty and an fdisk returned:

"Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)"

What's going on here?

2. How can I get the array to come up after a reboot? What needs to be
done? Do I need an rc script that runs mdadm?

Thanks,

Andy