HP P3410A HP NetRAID 1M/2M Installation & Configuration - Page 24
RAID 5: Striping with Distributed Parity
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Chapter 2 RAID Overview RAID 5: Striping with Distributed Parity RAID 5 is the most common configuration because it provides good overall performance and data protection with a minimum loss of storage capacity. RAID 5 distributes the parity blocks equally among all disk drives. If you have five physical drives configured as one RAID 5 logical drive, data blocks are written as follows: Stripe 1 Stripe 2 Stripe 3 Disk 1 Block 1 Block 5 Block 9 Disk 2 Block 2 Block 6 Block 10 Disk 3 Block 3 Block 7 Parity 9-12 Disk 4 Block 4 Parity 5-8 Block 11 Disk 5 Parity 1-4 Block 8 Block 12 RAID 5 outperforms RAID 1 for read operations. The write performance, however, may be slower than RAID 1, especially if most writes are small and random. For example, to change Block 1 in the diagram above, the HP NetRAID-1M or 2M adapter must first read Blocks 2, 3, and 4 before it can calculate Parity Block 1-4. Once it has calculated the new Parity Block 1-4, it must write Block 1 and Parity Block 1-4. RAID 5 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 the RAID 5 logical drive is reserved to store redundant data. • RAID 5 outperforms RAID 1 for read operations. • RAID 5 gives good performance if you have a high volume of small, random transfers. RAID 5 Disadvantages • Write performance is slower than RAID 0 or RAID 1. RAID 5 Summary • Choose RAID 5 if cost, availability, and performance are equally important. RAID 5 performs best if you have I/O-intensive, high read/write ratio applications such as transaction processing. 16