HP A7143A RAID160 SA Controller Support Guide

RAID Technology Overview
HP RAID160 SA Controller Supported RAID Configurations
Chapter 1 23
• More disk drive capacity usable than with RAID 1+0—parity
information only requires the storage space equivalent to one
physical disk on the array
Disadvantages
• Relatively low write performance
• Loss of data if a second disk fails before data from the first failed disk
is rebuilt
RAID ADG—Advanced Data Guarding
RAID ADG is similar to RAID 5 in that parity data is generated (and
stored) to protect against data loss caused by physical disk failure. With
RAID ADG, however, two different sets of parity data are generated for
each data block on a stripe, then the two parity data blocks are stored on
different physical disks allowing data to be preserved even if two
physical disks fail simultaneously. As can be seen in Figure 1-8,
“Advanced Data Guarding (RAID ADG),” the two sets of parity data
require as much storage capacity as the data blocks they correspond to
on each stripe in a logical drive.