Vedin, that's not how RAID operates at all, please read an FAQ instead of posting "what you've heard." That being said here's a general review, a RAID 0 array improves performance by splitting data and sending half, one fourth, ect (depending on the number of disks in an array) and theoretically improves performance by 100% in terms of data transfers, however in real life its more like 70-80% improvement with a good controller card. RAID 1 which is just mirroring does not improve performance at all as all it does is copy any contents of one drive to another, esentially making a backup copy. then there are various other array formats 2,3,4,5,ect and to find out about those check an FAQ, AnandTech did a good job in their explanation....