Introduction to RAID : RAID Levels : RAID 5

RAID 5

RAID 5 includes disk striping at the block level and parity. Parity is the data’s property of being odd or even, and parity checking detects errors in the data. In RAID 5, the parity information is written to all drives. RAID 5 is best suited for networks that perform many small I/O transactions simultaneously.

RAID 5 addresses the bottleneck issue for random I/O operations. Because each drive contains both data and parity, numerous writes can take place concurrently.

The following table provides an overview of RAID 5. The following figure provides a graphic example of a RAID 5 drive group.

Table 9. RAID 5 Overview

Uses

Provides high data throughput, especially for large files. Use RAID 5 for transaction-processing applications because each drive can read and write independently. If a drive fails, the Nytro MegaRAID controller uses the parity drive to re-create all missing information. Use also for office automation and online customer service that requires fault tolerance. Use for any application that has high read request rates but low write request rates.

Strong points

Provides data redundancy, high read rates, and good performance in most environments. Provides redundancy with lowest loss of capacity.

Weak points

Not well-suited to tasks requiring many writes, especially when no cache is used (clustering). Drive performance is reduced if a drive is being rebuilt. Environments with few processes do not perform as well because the RAID overhead is not offset by the performance gains in handling simultaneous processes.

Drives

3 through 32

Figure 13. RAID 5 Drive Group with Six Drives