Appendix B: Understanding RAID ● 102
RAID 6 Arrays
A RAID 6 array—also known as dual drive failure protection—is similar to a RAID 5 array
because it uses data striping and parity data to provide redundancy. However, RAID 6 arrays
include two independent sets of parity data instead of one. Both sets of parity data are striped
separately across all disk drives in the array.
RAID 6 arrays provide extra protection for your data because they can recover from two
simultaneous disk drive failures. However, the extra parity calculation slows performance
(compared to RAID 5 arrays).
RAID 6 arrays must be built from at least four disk drives. Maximum stripe size depends on
the number of disk drives in the array.
RAID 60 Arrays
Similar to a RAID 50 array (see page 101), a RAID 60 array—also known as dual drive failure
protection—is built from eight disk drives configured as two or more RAID 6 arrays, and
stripes stored data and two sets of parity data across all disk drives in both RAID 6 arrays.
Two sets of parity data provide enhanced data protection, and striping improves performance.
RAID 60 arrays also provide high data transfer speeds.
Disk Drive 1
Disk Drive 2
Disk Drive 3
Disk Drive 4
250 GB
250 GB
400 GB
400 GB
Drive Segment Size
(Smallest Disk Drive)
Disk Drive 2
Disk Drive 3
Disk Drive 4
Disk Drive 1
1 P1 ... P2
2 P2 ... 449
P1 3 ... P1
P2 4 ... 500
Unused Space = 150 GB
Disk Drives in Logical Drive Based on the drive segment sizes used:
RAID 6 Logical Drive = 500 GB plus
parity (P1 & P2)
Unused Space = 150 GB
