Explaining raid devices in the raid setup report – HP LeftHand P4000 Virtual SAN Appliance Software User Manual

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Table 7 Descriptions of RAID levels (continued)

Description

RAID level

provides a backup copy of the files and normal system
operations are not interrupted.

Offers the best combination of data protection and
performance. RAID 1+0 or drive mirroring creates fault

RAID 1+0 – Mirroring and Striping

tolerance by storing duplicate sets of data on a minimum
of four hard drives. There must be an even number of drives
for RAID 1+0. RAID 1+0(10) and RAID 1 are the most
costly fault tolerance methods because they require 50
percent of the drive capacity to store the redundant data.
RAID 1+0(10) 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(10) 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