The Myth box here is our most recently set-up system with RAID.
It has two 300GB drives, each of which has a small 8GB partition, and a huge 292GB partition.

The first drive hold the 8GB root partition (bootable non-RAID), and the second drive holds the 8GB swap partition (non-RAID). The two BIG partitions are then combined with RAID0 to give the box about 584GB of fast storage space for recordings.

No redundancy in this one -- I don't care too much about losing TV recordings. The RAID0 was more important because the box needs the I/O bandwidth to handle simultaneous recording of up to two HD 1080i streams along with two analog streams, while doing playback of another HD 1080i stream.

CPU never gets busy, but the hard drives sure do.

Cheers