A storage technology that distributes data across a group of physically separate hard drives configured as a single logical memory unit. As RAID stores all data on redundant drives, it provides a considerable level of fault tolerance. RAID may involve drives on multiple servers in a cluster connected via a storage area network (SAN). A simpler and less expensive approach is known as just a bunch of disks (JBOD), which essentially is a bunch of disk drivers not configured as a RAID. See also JBOD, SAN, and server.