10.5 HP StoreVirtual Storage User Guide (AX696-96269, March 2013)

Table 6 Descriptions of RAID levels (continued)
DescriptionRAID level
method because it requires 50 percent of the drive capacity
to store the redundant data. RAID 1+0 first mirrors each
drive in the array to another, and then stripes the data
across the mirrored pair. If a physical drive fails, the mirror
drive provides a backup copy of the files and normal
system operations are not interrupted. RAID 1+0 can
withstand multiple simultaneous drive failures, as long as
the failed drives are not mirrored to each other.
Offers the best combination of data protection and usable
capacity while also improving performance over RAID 6.
RAID 5
RAID 5 stores parity data across all the physical drives in
the array and allows more simultaneous read operations
and higher performance. If a drive fails, the controller uses
the parity data and the data on the remaining drives to
reconstruct data from the failed drive. The system continues
operating with a slightly reduced performance until you
replace the failed drive. RAID 5 can only withstand the
loss of one drive without total array failure. It requires an
array with a minimum of three physical drives. Usable
capacity is N-1 where N is the number of physical drives
in the logical array.
Offers the best data protection and is an extension of RAID
5. RAID 6 uses multiple parity sets to store data and can
RAID 6
therefore tolerate up to 2 drive failures simultaneously.
RAID 6 requires a minimum of 4 drives. Performance is
lower than RAID 5 due to parity data updating on multiple
drives. RAID 6 uses two disk for parity; its fault tolerance
allows two disks to fail simultaneously. Usable capacity is
N-2 where N is the number of physical drives in the logical
array.
Explaining RAID devices in the RAID setup report
In the Storage category, the RAID Setup tab lists the RAID devices in the storage system and provides
information about them. An example of the RAID setup report is shown in Figure 8 (page 29).
Information listed in the report is described in Table 7 (page 30).
Figure 8 RAID setup report
RAID devices by RAID type
Each RAID type creates different sets of RAID devices. Table 7 (page 30) contains a description
of the variety of RAID devices created by the different RAID types as implemented on various
storage systems.
Explaining RAID devices in the RAID setup report 29