How do I set up raid. Why not just ask how to write a kernel from scratch :P j/k RAID can be quite comlpicated to get to work properly.
I'm not versed on the way the Fedora installer handles it, so I won't speak to that, I'll just give you some general information.
For speeding up data access you'll want to use RAID 1. This size is a great
guide to Raidlevels http://www.acnc.com/04_01_01.html
RAID 1 will stripe data across both drives. If you want speed increase I'd go with RAID 1, if you're looking for fault tolerance you can go with RAID 0.
Now, since you only have 5 GB drives I assume you're running a desktop machine and not a server ? What is the system ? Are you running dual 64 bit processors or an old clunky Pentium II ? How much RAM do you have ? Can your hard disk controller perform two concurrent read operations ? If not, RAID is essentially useless becasue it will have to read from one drive and then the other, but you want to read from both at the same time to get any performance increase.
Unless you have a hefty system you probably won't notice much if any speed increase from the RAID. Remember, RAID only has to do with how data is stored on the hard disks and as such, will only speed up disk access (or in the case of RAID 0 provide redundancy in case of data loss). It won't increase the efficiency of computations per se.
PS It's basically a choice: do you want the headache of trying RAID or not? Here's an example of what's in store (though this guide's for Slackware):
PPS This post all has to do with software RAID. If you want hardware RAID (i.e., you go and buy a RAID controller card) it will be very simple to set and faster since the controller card can read from multiple disks simultaneously (that's what it's designed to do in the first place) but not free...far, far from free