This level of RAID involves striping, where reads and writes of sectors of data are interleaved between multiple drives. Essentially, the workload is balanced between all the drives in the array, so performance is increased. It is recommended that you use identical hard drives for the greatest increase in performance. Although it is recommended, it is not necessary. The disk array capacity is equal to the number of drives times the smallest drive. The speed of the array will depend on the speed of the slowest hard drive. So for example, using a 10 GB and a 20 GB hard drive will create a 20 GB disk array. That's a lot of wasted space, so using two identical drives is definitely the way to go. Performance in RAID 0 is also determined by the stripe size used. The Promise FastTrack66 allowed you to specify a stripe size, which is the size chunks to interleave on the hard drives. Larger stripe sizes may be better for video editing and large file movement, while smaller stripe sizes might be better for everyday apps. Since the Iwill card does not let you specify the size, I assume it defaults to 16kb. A disadvantage of this level is that if one of the drives fail, the entire array is lost.

This level of RAID involves data mirroring, where duplicate data is written to a pair of drives while reads are performed in parallel. Fault tolerance is introduced here since each drive of the mirrored pair is installed on separate connectors. So, when one drive fails, the other one is still up with the data. You can rebuild the data of the damaged drive during reboot. Because both drives have the same data, the actual capacity will be half the total capacity of both drives. Again, if the drives differ in size, the larger drive will have wasted space. The workload is again distributed here to provide an increase in performance. However, it's not as high as the performance increase with RAID 0.

This level is basically a blend of the above two levels. It offers the same performance boost as RAID 0 while having the redundancy and mirroring capabilities of RAID 1. A minimum of 4 drives are needed to implement this since two pairs of drives are striped and those are mirrored on the remaining two drives. The major disadvantage of this is that it's expensive. To get the best performance you need 4 identical drives.