Thx for this.  Successfully used your guide to setup Juanty 9.04 with RAID5.

Points to note, RAID5 will NOT work when boot partition is raid5.  For example, if you have:

md0 = swap

md1 = root (boot within root)

Then you will not be able to write your grub properly to each drive due to raid5 not having separate copies of files on each disc.  Grub boots at disk level and not at software raid level it seems.

My work around was to have boot separate. I chose:

md0=swap (3x drives within raid5, sda1, sdb1, sdc1)

md1=boot (2x drives within raid1, sda2, sdb2) 3rd drive is not needed unless 2 drives fail at once, and because drives a mirrored completely you are able to write to grub.

md2=root (3x drives within raid5, sda3, sdb3, sdc3)

I'll be writing my own guide for raid1 and raid5 so you can see the difference in commands, but will referrence this guide a lot as it helped me the most out of all the ubuntu raid guides i found on google.

Watch http://www.richardbignell.co.uk/ for new guides.