crazijoe

I would be very leary to adding another disk to an existing striped array. I haven't had a chance to really play around with Intel matrix arrays. From my experience, you have to create a new array with the new disk. Thus loosing everything off the original array.
IMHO. If you need more space, put your data on a separate drive. I don't like to preach but I cannot emphisize enough on the risk of a striped array. I have 4 WD Raptor drives in a RAID 0 array. Within a 2 year span, I have had 3 drives fail, 3 different times. The result, 3 different times the raid has failed because of a hdd failure. This does not include array failures from read/write errors. The more drives in a RAID the more chances of failure. My general rule of thumb is to keep your OS and apps on the striped array and keep your data on a separate drive. Be it a RAID 1, RAID 5, etc. Just do not keep critical data on a RAID 0 array.
Also generally RAID 5 should be used for data and not for the OS. RAID 5 usually has slower write performance than a RAID 1 because of the parity checking. The nice thing about RAID 5 is the ability to rebuild itself "On the Fly".