RAID is like slapping 2(or more) HD's together to woork as one, it can provide different effects depending on the raid type
in raid 0 the controller card writes info to every other drive, so all the even stripes of data will be on one drive, and the odds on the other. this allows the drives to work (theoretically) twice as fast.
breakdown of raid types:
RAID0- writes every other stripe of data on each drive,
the idea is to strap 2 hard drives together so they can
go 2 times as fast (they dont actually perform THAT
fast). if you lose 1 drive than you lose all info on
both drives(ie: have to reformat)
50G+50G=100G
RAID1- writes exact same thing on 2 drives. gives you a
copy incase one drive crashes. (if partition is damaged
again it will probly happen on both drives. dsnt
improve performance, but gives you a backup.
50G+50G=50G
RAID5-takes 3 drives. it's like best of both worlds.
stripes of data rotate on 2 drives and 3rd gets a
"parity note" it allows you to take data from any 2
drives and recreate the data on the 3rd.
50G+50G+50G=100G
you could also just set up the drive independent of
each other and you wouldnt have to worry about
anything, you get regular performance, and no backup,
will show as 2 drives
50G+50G= 2 50G drives
RAID 1+0 takes 4 drives. it's exacly like it sounds.
take 2 drives in raid 0 for performance, and uses 2
more drives to make a copy of each to give you back up.
50Gx4 = 100G
you can find out more info in the
Anandtech FAQ's
or if you have a specific question post it here.