Why is my new RAID Setup so slow ?

I don't know about raid on ATA so I'm assuming you have SATA drives. do you know if the drives are SATA I, II, etc? One is only 5400 RPM which is pretty darn slow, and they're laptop drives. I was thinking on doing a RAID array in my upcoming build, would think that its best to get two identical drives at least 7200 RPM. also, striped is RAID 0, mirror RAID 1, striped mirror is probably RAID 10. or 1+0, same thing.