Raid 3 - Block Striping With Dedicated Parity - Promise Technology VTRAK 15200 User Manual

VTrak 15200 User Manual
RAID 3 – Block Striping with Dedicated Parity
RAID level 3 organizes data across the disk drives of the logical drive, and stores
parity information on to a disk drive dedicated to this purpose. This organization
allows increased performance by accessing multiple disk drives simultaneously
for each operation, as well as fault tolerance by providing parity data. In the event
of a disk drive failure, data can be re-calculated by the RAID system based on the
remaining data and the parity information.
The adjustable block size of the RAID 3 logical drive allows for performance
tuning based on the typical I/O request sizes for your system. The block size
must be set at the time the logical drive 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.
Figure 3. RAID 3 Stripes data and adds a dedicated Parity Drive
The capacity of a RAID 3 logical drive is the smallest drive size multiplied by the
number of disk drives less one. Hence, a RAID 3 logical drive with (4) 100 GB
disk drives will have a capacity of 300GB. A logical drive with (2) 120GB disk
drives and (1) 100GB disk drive will have a capacity of 200GB.
RAID 3 logical drives on VTrak consist of 3 to 15 disk drives.
Data Stripes
Data Drives
192
Parity Drive