Redundant Array of Independent (or Inexpensive) Disks, a category of disk drives that employ two or more drives in combination, for fault tolerance and performance.
RAID disk drives are used frequently on servers. Among the varied levels of RAID that exist, Oracle suports the following:
Level : Striped Disk Array without Fault Tolerance: Provides data striping (spreading out blocks of each file across multiple disk drives) but no redundancy. This improves performance, but does not deliver fault tolerance. If one drive fails then all data in the array is lost.
Level 1: Mirroring and Duplexing: Provides disk mirroring. Level 1 provides twice the read transaction rate of single disks, and the same write transaction rate as single disks.
Level 5: Block Interleaved Distributed Parity: Provides data striping at the byte level and also stripe error correction information. This results in excellent performance and good fault tolerance. Level 5 is one of the most popular implementations of RAID.