Adaptec 4000SAS - RAID 6 Arrays

Appendix B: Understanding RAID ● 87
RAID 6 Arrays
Note: RAID 6 is an upgrade feature; if the RAID 6 feature is locked, see
Adding Enhanced Features on page 20 for information on purchasing a
feature key.
A RAID 6 array 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 four or more disk drives, to a
maximum of sixteen. Maximum stripe size depends on the number of
disk drives in the array.
Disk Drive 1
Disk Drive 2
Disk Drive 3
Disk Drive 4
250 GB
250 GB
400 GB
400 GB
D
isk Drives in Logical Drive
Disk Drive 1
Disk Drive 2
Disk Drive 3
Disk Drive 4
RAID 6 Logical Drive = 500 GB plus Parity (P1 & P
2)
1
2
P1
P2
Not Used
Not Used
P1
P2
3
4 500
P1
449
P2...
...
...
...
Unused Space: 150 GB
Unused Space: 150 GB
Drive Segment Size (Smallest Disk Drive)