Raiding for an Explanation of RAID Page 3
RAID 1 Mirroring
The unfortunate, obvious downside to RAID 1 is the loss in capacity. As noted, two 5 GB disks in a RAID 1 array appear as a single 5 GB disk. Although the increased reliability of this method cannot be disputed, the halving of disk space translates into increased cost.
Again, when using RAID mirroring, the size of the disk is equal to the capacity of the smallest disk. Using a 1 GB and 10 GB disk in a RAID 1 array is unwise, as it will appear as only a 1 GB disk the remaining 9 GB on the 10 GB drive cannot be used. Given that, use only disks identical in size and performance in a RAID 1 array.