User Manual

Appendix
A-7
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