Promise Technology UltraTrak100 TX8 - Manual (Page 50)

UltraTrak100 TX4 and UltraTrak100 TX8
User Manual
44
RAID 3 – B
LOCK
S
TRIPING WITH
P
ARITY
D
RIVE
RAID level 3 organizes data across the physical drives of the array, and stores
parity information on to a drive dedicated to this purpose. This organization allows
increased performance by accessing multiple drives simultaneously for each
operation, as well as fault tolerance by providing parity data. In the event of a hard
drive failure, data can be re-calculated by the RAID system based on the
remaining drive data and the parity information.
The adjustable block size of the RAID 3 array allows for performance tuning based
on the typical I/O request sizes for your system. The block size must be set at the
time it is created and cannot be adjusted dynamically. Generally, RAID Level 3
tends to exhibit lower random write performance due to the heavy workload going
to the dedicated parity drive for parity recalculation for each I/O.
The capacity of a RAID 3 array is the smallest drive size multiplied by the number
of drives less one. Hence, a RAID 3 array with (4) 1.0 GB hard drives will have a
capacity of 3.0GB. An array with (2) 1.2GB hard drives and (1) 1.0GB hard drive
will have a capacity of 2.0GB.
Figure A4. RAID 3 multiple drives stripe data w/ one dedicated parity drive