When creating RAID 10 or RAID 50 multi-level RAID arrays using mixed drive sizes the resulting Virtual Disk is a concatenated array.
The PERC 5 User Guide states that each array will be reduced in size based on the size of the smallest array member. This applies only to the Primary RAID Level (RAID 0, 1, 5) and does not take into account multi-level RAID arrays (RAID 10, 50). In a RAID 10 or RAID 50 array each of the Primary RAID Levels is reduced in size based on the smallest array member. In the RAID 10 or RAID 50 array, if the Primary RAID Levels are different sizes, they will be concatenated together rather than being striped together.
For example: Three 500GB drives and one 250GB drive are used to create a RAID 10 (Figure 1). The result would be:
Figure 1: Example of RAID 10