This is a quick sum up on the setup of Software RAID in linux. If your output came out as shown, your device is set to DMA Mode. This level converts all of the disks in the array into one large disk. It is twice as fast as the disk's speed but has no fault tolerance. One disk becomes an exact mirror of the other, so there is greater fault tolerance.
Speed is equivalent to the slowest drive in the array.
You have one large disk, but parity infomation is distributed among the disks. You will have speeds between the fastest and slowest disks and fault tolerance. Run 'df -h' to see the results. And that is how its done.