I know this is an old post but some things have changed since 10.04
I am currently using 12.04
By default with a regular ubuntu installation in a pc with a single drive is to have the partitions: the main partition (sda1) and an extended partition (sda2) which contains the swap partition (sda5)
Can anybody confirm that is only need to create two (and not three) raid-arrays, md1 and md5 which correspond to sda1 <-> sdb1 and sda5 <-> sdb5 ?
Please let me know if you need further information!