Appendix B: Selecting the Best RAID Level
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160
RAID 6 Logical Drives
A RAID 6 logical drive—also referred to as
dual drive failure protection
—is similar to a RAID 5
logical drive because it uses data striping and parity data to provide redundancy. However,
RAID 6 logical drives include
two
independent sets of parity data instead of one. Both sets of
parity data are striped separately across all disk drives in the logical drive.
RAID 6 logical drives 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 logical drives).
RAID 6 logical drives must be built from at least four disk drives. Maximum stripe size
depends on the number of disk drives in the logical drive.
RAID 60 Logical Drives
Similar to a RAID 50 logical drive (see
page 159
), a RAID 60 logical drive—also referred to as
dual drive failure protection
— is built from at least eight disk drives configured as two or more
RAID 6 logical drives, and stripes stored data and two sets of parity data across all disk drives in
both RAID 6 logical drives.
Two sets of parity data provide enhanced data protection, and striping improves performance.
RAID 60 logical drives 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
Unused Space = 150 GB
= 500 GB plus Parity (P1 & P2)
RAID 6
Logical Drive
