HP LC2000r HP NetRAID 1M/2M Installation & Configuration - Page 26

Chapter 2 RAID Overview RAID 10 Disadvantages • Costs are high, because 50% of all disk space is allocated for redundancy. • Capacity expansion is an offline operation only. RAID 10 Summary • RAID 10 provides the best performance for most applications where redundancy and large logical drive size are required, and cost is not a factor. RAID 50: Spanning with Distributed Parity A RAID 50 configuration combines multiple RAID 5 arrays into a single storage space. A distributed parity algorithm within each RAID 5 array provides data redundancy. The data is striped across all the RAID 5 arrays that constitute the RAID 50 logical drive. For example, if your RAID 50 configuration spans two RAID 5 arrays, data blocks are written as follows: Stripe 1 Stripe 2 Stripe 3 Spanned Array (RAID 50) Array 1 (RAID 5) Array 2 (RAID 5) Disk 1 Block 1 Block 7 Block 13 Disk 2 Block 2 Block 8 Parity 13-15 Disk 3 Block 3 Parity 7-9 Block 14 Disk 4 Parity 1-3 Block 9 Block 15 Disk 5 Block 4 Block 10 Block 16 Disk 6 Block 5 Block 11 Parity 16-18 Disk 7 Block 6 Parity 10-12 Block 17 Disk 8 Parity 4-6 Block 12 Block 18 RAID 50 Advantages • There is no data loss or system interruption due to disk failure, because if one disk fails, data can be rebuilt. • Capacity equivalent to only one disk in each array of the RAID 50 logical drive is required to provide redundancy. • RAID 50 lets you create large logical drives: ♦ With the HP NetRAID-1M adapter, the total number of disks in the RAID 50 logical drive is limited by the number of disks that can be attached to its single SCSI channel. For example, if a Rack Storage/12 enclosure is used, the maximum number of disks in a RAID 50 logical drive is 12. 18