Raid 3 - Block Striping With Parity Drive - Promise Technology SuperTrak SX6000 User Manual

SuperTrak SX6000™ User Manual Appendix C
Figure 17 Raid 0+1 Striping and Mirroring of Two Drive Pairs
RAID 3 – Block Striping with Parity Drive
RAID level 3 organizes data across the physical drives of the array, and stores parity
information onto 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.
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