User guide

Understanding Drive Arrays D-7
Distributed Data Guarding (RAID 5)
Distributed data guarding also called RAID 5, stores parity data across all the
drives in the array. Spreading the parity across all the drives allows more
simultaneous read. If a drive fails, the controller uses the parity data and the
data on the remaining drives to reconstruct data from the failed drive. This
allows the system to continue operating with slightly reduced performance
until you replace the failed drive.
Distributed data guarding requires an array with a minimum of three physical
drives and allows a maximum of 15 drives. Therefore, in an array containing
three physical drives, distributed data guarding uses only 33 percent of the
total logical drive storage capacity for fault tolerance, while a 15-drive
configuration uses only 7 percent.
DATA
P
P
P
P
P
P
P
P
P
DATADATADATA
P = Parity
WAR2-053.AI, 9-3.EPS
Figure D-5. Distributed Data Guarding distributes the redundant data [P]
throughout the physical drives