IDE = Standard speed & redundancy, if the drive fails...you lose everything on that drive.
RAID Mirrored = increased redundancy but slightly slower speed....if one drive fails, you have a backup.
RAID Striped = increased speed but if one drive fails, you lose everything.
RAID-1, mirrored, does increase speed over normal ide but you sacrifice an entire HDD of space
RAID-0, striped, also increases speed over normal ide but you sacrifice data security
Any RAID array increases read performance as now you have two read heads working simultaneosly
but RAID-0 also increases write speeds because the head also write different things simultaneously too while RAID-1 is just as fast as normal IDE at writing because the write heads imitate each other.