Promise Technology FastTrak SX4000 Lite User Manual download pdf (Page 53)

Chapter 5: Disk Array Concepts

Block and Parity Striping (RAID 5)

RAID 5 calculates parity in order to achieve redundancy rather than writing a

second copy of the data, like RAID 1. Parity is distributed across the physical

drives along with the data blocks. In each case, the parity data is stored on a

different disk than its corresponding data block.

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.

a parity

b parity

c parity

d parity

Disk Drives

Distributed Parity

Data

Blocks

Figure 17. RAID 5 Stripes all Drives with Data and Parity Information

The capacity of a RAID 5 array is the smallest drive size multiplied by the total

number of drives, minus one. Hence, a RAID 5 array with four 100 GB hard

drives will have a capacity of 300 GB. An array with two 120 GB hard drives and

one 100 GB hard drive will have a capacity of 200 GB.

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Promise Technology FastTrak SX4000 Lite User Manual Page 53