RAID 3 (Redundant Array of Independent Disks Level 3) is one of several related specifications for a data storage system that uses disk mirroring, disk striping and parity checking to provide redundancy and fault-tolerance in data storage systems, as well as improving performance. RAID schemes are most commonly applied to hard disk drives.

The RAID 3 scheme, "Parallel transfer with parity", requires a minimum of 3 drives to implement. Data blocks are striped across each disk in the RAID array. Parity is maintained by generating stripe parity after each Write, and recorded on one or more dedicated parity disks. Parity is then checked on each Read.

Advantages of RAID 3
  • Very high Read transfer rate
  • Very high Write transfer rate
  • Disk failure has a minimal impact on throughput
  • Low ratio of ECC (parity) disks to data disks, allowing for greater efficiency

Disadvantages of RAID 3
  • Transaction rate equal to that of a single disk drive at best (if spindles are synchronized)
  • Controller design is complex
  • Very difficult and resource intensive to do as a software RAID system

Applications RAID 3 works well for