Integrated Dell Remote Access Controller 9 (iDRAC9) Version 3.00.00.00 User's Guide

RAID level 6-striping with additional distributed parity

RAID 6 provides data redundancy by using data striping in combination with parity information. Similar to RAID 5, the parity is distributed within each stripe. RAID 6, however, uses an additional physical disk to maintain parity, such that each stripe in the disk group maintains two disk blocks with parity information. The additional parity provides data protection in the event of two disk failures. In the following image, the two sets of parity information are identified as P and Q.

RAID 6 characteristics:

• Groups n disks as one large virtual disk with a capacity of (n-2) disks.
• Redundant information (parity) is alternately stored on all disks.
• The virtual disk remains functional with up to two disk failures. The data is reconstructed from the surviving disks.
• Better read performance, but slower write performance.
• Increased redundancy for protection of data.
• Two disks per span are required for parity. RAID 6 is more expensive in terms of disk space.