redundancy

1. Additional information stored along with user data that enables a controller to reconstruct lost data. Redundant Array of Independent Disks (RAID) 1 uses mirroring for redundancy. RAID 3, RAID 5, and RAID 6 use redundancy information, sometimes called parity, that is constructed from the data bytes and is striped along with the data on each drive. 2. The use of trays that are not necessary for normal system operation. The trays are substituted for another component or can perform the same function as another component. This use allows the system to remain operational if the component fails.