Appendix B: Understanding RAID ● 80RAID 50 ArraysA RAID 50 array is built from six to forty-eight disk drives configured as two or more RAID 5arrays, and stripes stored data and parity data across all disk drives in both RAID 5 arrays. (Formore information, see RAID 5 Arrays on page 78.)Note: Because they support four disk drives only, the ICP9047MA RAID controller can’tsupport RAID 50 arrays.The parity data provides data protection, and striping improves performance. RAID 50 arraysalso provide high data transfer speeds.Drive segment size is limited to the size of the smallest disk drive in the array. For example,three 250 GB disk drives and three 400 GB disk drives comprise two equal-sized RAID 5 arrayswith 500 GB of stored data and 250 GB of parity data. The RAID 50 array can therefore contain1000 GB (2 x 500 GB) of stored data and 500 GB of parity data.In this figure, P represents the distributed parity data.RAID 5BRAID 50Logical Drive=1000 GBplus ParityRAID 5AEach RAID 5 Logical Drive has500 GB Data Storage250 GB Parity DataDrive 1250 GBDrive 2250 GBDrive 3250 GB Drive 4400 GBDrive 5400 GBDrive 6400 GB1, 5, P 3, P, 9 P, 7, 11 2, 6, P 4, P, 10 P, 8, 12 Total UnusedSpace = 150 GB
