System information

Appendix
A-6
A.6 RAID 6
RAID 6 stripes data and parity data across an array of drives, as with RAID 5, and calculates two sets of parity
information for each stripe to improve fault tolerance. Performance-wise, RAID 6 is generally slightly worse than RAID 5
in terms of writes, due to the extra parity calculations. It may, however, be slightly faster in terms of random reads, due to
the spreading of data over one more disk. As with RAID 3 and RAID 5, performance can be adjusted by changing stripe
size.
RAID 6: Independent data disks with double parity blocks
Characteristics
• Storage capacity = (number of disks -2) x (capacity of the smallest disk)
• A minimum of four disks are required.
• Fault tolerance: very good to excellent
• Good speed with random reads
Recommended use
• File and application servers
• Database servers
• Internet, email and news servers
• Intranet servers
• Use in high reliability server environments
D
A B P1 P2
C P3 P4 D
P5 P6 E F
P7
Disk 1 Disk 2 Disk 3 Disk 4
G H P8
CONTROLLER
A
B
C
Figure A-5 RAID 6 disk array