20 OverviewThe parity data is distributed across all the physical disks in the system. If asingle physical disk fails, it can be rebuilt from the parity and the data on theremaining physical disks. RAID level 5 combines distributed parity with diskstriping, as shown in Figure 2-3. Parity provides redundancy for one physicaldisk failure without duplicating the contents of entire physical disks.RAID 6 combines dual distributed parity with disk striping. This level ofparity allows for two disk failures without duplicating the contents of entirephysical disks.Figure 2-3. Example of Distributed Parity (RAID 5)NOTE: Parity is distributed across multiple physical disks in the disk group.Figure 2-4. Example of Dual Distributed Parity (RAID 6)NOTE: Parity is distributed across all disks in the array.Stripe element 1Stripe element 7Stripe element 2Stripe element 8Stripe element 3Stripe element 9Stripe element 4Stripe element 10Stripe element 5Parity (6–10)Parity (11–15)Parity (1–5)Stripe element 6Stripe element 12Stripe element 15 Stripe element 11Stripe element 14Stripe element 13Stripe element 19Stripe element 25Stripe element 20Stripe element 23Stripe element 18Stripe element 21Stripe element 16Stripe element 22Stripe element 17Parity (21–25)Parity (26–30)Parity (16–20)Stripe element 24Stripe element 30Stripe element 27 Stripe element 29Stripe element 26 Stripe element 28Stripe element 1Stripe element 5Stripe element 2Stripe element 6Stripe element 3Parity (5–8)Stripe element 4Parity (5–8)Parity (1–4)Stripe element 7Stripe element 10Parity (1–4)Stripe element 8Stripe element 12Stripe element 9 Stripe element 11Parity (9–12)Parity (9–12)Stripe element 13 Stripe element 14 Stripe element 16Parity (13–16) Stripe element 15Parity (13–16)
