Dell PowerEdge RAID Controller H700 - Manual (Page 20)

20 Overview
The parity data is distributed across all the physical disks in the system. If a
single physical disk fails, it can be rebuilt from the parity and the data on the
remaining physical disks. RAID level 5 combines distributed parity with disk
striping, as shown in Figure 2-3. Parity provides redundancy for one physical
disk failure without duplicating the contents of entire physical disks.
RAID 6 combines dual distributed parity with disk striping. This level of
parity allows for two disk failures without duplicating the contents of entire
physical 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 1
Stripe element 7 Stripe element 2
Stripe element 8 Stripe element 3
Stripe element 9 Stripe element 4
Stripe element 10
Stripe element 5
Parity (6–10)
Parity (11–15)
Parity (1–5)
Stripe element 6
Stripe element 12 Stripe element 15 Stripe element 11 Stripe element 14 Stripe element 13
Stripe element 19
Stripe element 25
Stripe element 20
Stripe element 23
Stripe element 18
Stripe element 21
Stripe element 16
Stripe element 22
Stripe element 17
Parity (21–25)
Parity (26–30)
Parity (16–20)
Stripe element 24
Stripe element 30 Stripe element 27 Stripe element 29 Stripe element 26 Stripe element 28
Stripe element 1
Stripe element 5 Stripe element 2
Stripe element 6 Stripe element 3
Parity (5–8)
Stripe element 4
Parity (5–8)
Parity (1–4)
Stripe element 7
Stripe element 10
Parity (1–4)
Stripe element 8
Stripe element 12 Stripe element 9 Stripe element 11 Parity (9–12) Parity (9–12)
Stripe element 13 Stripe element 14 Stripe element 16 Parity (13–16) Stripe element 15 Parity (13–16)
PERC7.2_UG.book Page 20 Thursday, March 3, 2011 2:14 PM