Users Guide

RAID 5 characteristics:
• Groups n disks as one large virtual disk with a capacity of (n-1) disks.
• Redundant information (parity) is alternately stored on all disks.
• When a disk fails, the virtual disk still works, but it is operating in a degraded state. The data is reconstructed from the surviving
disks.
• Better read performance, but slower write performance.
• Redundancy for protection of data.
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.
RAID level 50 (striping over RAID 5 sets)
RAID 50 is striping over more than one span of physical disks. For example, a RAID 5 disk group that is implemented with three
physical disks and then continues on with a disk group of three more physical disks would be a RAID 50.
It is possible to implement RAID 50 even when the hardware does not directly support it. In this case, you can implement more than
one RAID 5 virtual disks and then convert the RAID 5 disks to dynamic disks. You can then create a dynamic volume that is spanned
across all RAID 5 virtual disks.
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