If you have a current system running smooth but is running out of spaces, you might consider to add a new hard drive to it. Or, you can add a software RAID 5 to the current system under Ubuntu is very easy. Here, I will not show you how to do it but Jonny will show you on his blog.
The following is not required for Ubuntu 7.04 as it will generated automatically :
sudo echo “DEVICE partitions” > /etc/mdadm/mdadm.conf
sudo mdadm –detail –scan >> /etc/mdadm/mdadm.conf