I have already 2 raid arrays md0 and md1, I am now trying to make a raid5 array out of three 250Gb sata disks.

So i run on all the disks:
"sudo fdisk /dev/sda"
delete any filesystem that might be present, "d" (theese are old disks)
make a new partition "n" using the full disks capacity.
change type "t" to linux raid autodetect "fd"
Then write changes and exit.

Then i set up mdadm:
"sudo mdadm --create /dev/md2 --level=5 --raid-devices=3 /dev/sda /dev/sdb /dev/sdc"

This works fine and the array starts with 2 disks and one spare and immediately starts rebuilding the spare.

I can check the progress with:
sudo mdadm -D /dev/md2

After a while ubuntu stops responding. I have done this 4-5 times now and it always happens when rebuilding. I don't have any progress indication but based on the time it takes before it crashes and using the above command before it crashes tells me it must be around 50-60% done.

Only a hard reset will bring the computer back to life.

To the best of my knowledge the drives should be fine so i am starting to suspect the controller, witch is the onboard nforce4 controller.

Anyone have a clue to get this to work?

Now i seem to be inable to do anything else with the drives as any change to the partition table will be undone by mdadm at the next reboot, where it starts to rebuild the array again, deleting anything present on the drives, and thus starting the countdown to the inevitable crash automatically.

This is getting really frustrating!

first remove the raid info from the disks with fdisk
then do
mdadm --zero-superblock /dev/sda

Yep, that will remove the raid, i was hoping to get the raid to work though...