Accusys ExaRAID GUI - Manual (Page 261)

Appendix
A-5
A.4 RAID 3
In RAID 3, all data is divided into pieces, after which the system calculates
the parity of these pieces. The pieces are written to separate disks in
parallel with the writing of the parity data. In the event of disk failure, the
parity data can be used to rebuild the lost data. If two or more disks fail,
data will be lost. While the low ratio of parity disks to data disks ensures
high efficiency, the parity disk is accessed more frequently than other
disks, therefore making it unsuitable for random write access.
RAID 3: Parallel transfer with parity
Characteristics
• Storage capacity = (number of disks -1) x (capacity of the smallest disk)
• A minimum of three disks are required.
• Fault tolerance: Good
• The data block is striped, written on the data disks. Stripe activity is generated
on writes, recorded on the parity disk and checked on reads.
• Low ratio of (parity) disks to data disks ensures high efficiency.
Recommended use
• Video production and live streaming
• Image editing
• Video editing
• Any application requiring high throughput
A
A B P
AB
Hot Spare
C D P
CD
E F P
EF
B
C
G
F
D
E
CONTROLLER
Figure A-3 RAID 3 disk array