How RAID 5 affects performance

 

Learn about how performance is affected when using RAID 5 protection.

Device parity protection requires extra I/O operations to save the parity data. To avoid performance problems, all IOAs contain a nonvolatile write cache that ensures data integrity and provides faster write capability. The system is notified that a write operation is complete as soon as a copy of the data is stored in the write cache. Data is collected in the cache before it gets written to a disk unit. This collection technique reduces the number of physical write operations to the disk unit. Because of the cache, performance is generally about the same on protected and unprotected disk units.

Applications that have many write requests in a short period of time, such as batch programs, can adversely affect performance. Disk unit failures can adversely affect the performance for both read and write operations.

The additional processing that is associated with a disk unit failure in a parity set can be significant. The decrease in performance is in effect until both the failed disk unit is repaired (or replaced) and the rebuild process is complete. If device parity protection decreases performance too much, consider using mirrored protection.

 

Parent topic:

RAID 5 concepts