Promise Technology FASTTRAK SX4300 - Manual (Page 44)

FastTrak SX4300, SX8300 User Manual
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RAID 5 – Block Striping with Distributed Parity
RAID level 5 organizes data across the disk drives of the logical drive, and
distributes parity information across the disk drives along with the data blocks.
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 5 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.
RAID 5 makes efficient use of hard drives and is the most versatile RAID Level. It
works well for file, database, application and web servers.
Figure 3. RAID 5 Stripes all drives with data and parity information
The capacity of a RAID 5 logical drive is the smallest disk drive size multiplied by
the number of disk drives, less one. Hence, a RAID 5 logical drive with four 100
GB disk drives will have a capacity of 300 GB. A logical drive with two 120 GB
disk drives and one 100 GB disk drive will have a capacity of 200 GB.
RAID 5 logical drives on the FastTrak SX4300 consist of 3 or 4 disk drives.
RAID 5 logical drives on the FastTrak SX8300 consist of 3 to 8 disk drives.
Data
Blocks
Distributed Parity
Disk Drives