And then when the power goes out, lose any unsaved data?!?!
Uhh... no. Every single program I use that handles sensitive data saves in at least one-minute intervals.
I don't like RAID anyway. I have enough hard-drive space as it is.
I'm unaware of any RAID configuration that has the main intention of increasing capacity. RAID is used for write speed, drive integrity or a combination of the two.
In fact, with RAID 5 (At least 4 drives required), you entirely lose the functionality of one of the drives in the array for bit parity. The advantage is: if you lose one drive in the array, you lose
none of your data. When it is replaced, the array rebuilds itself. On top of that, RAID 5 features data striping, so writing data is a lot faster. There are tons of RAID configurations, but 5 is probably the most practical/reliable for a workstation situation.