RAID=Redundent Array of Inexpensive Disks RAID 0, combines areas of free space from up to 32 multiple hard disks into one logical volume. This volume optimizes performance by allowing data to be written to all the disks at the same rate. This volume is not fault-tolerant as well so if one disk in the volume fails, then all the data is lost RAID 1 Disk duplexing eliminates the single point of failure that exists in disk mirroring. This is done by adding another disk controller and configuring the RAID system to duplicate data on disk drives that are attached to two different disk controllers. There is generally no significant performance difference between disk mirroring and disk duplexing. The user is just adding further redundancy in the form of a second controller. The overhead of RAID 1 duplexing is 50 percent. RAID 5 requires a minimum of three disk drives to implement. The disk drives that comprise a RAID 5 solution are often referred to as a RAID 5 array. The failure of a single disk drive does not cause the network server to fail. The missing information that was on the failed disk can be recreated quickly using the information on the remaining disks. The failed disk drive should be replaced as quickly as possible. RAID 5 cannot survive the failure of a second disk drive after one disk drive has failed. Because of this fact, some RAID systems allow for the configuration of a "hot spare" disk drive in the RAID system. A hot spare disk drive is powered up and running, but it contains no data. It is just waiting for a drive in the disk array to fail so that it can be used. RAID 0/1, which is sometimes called RAID 0+1 or RAID 10, involves mirroring or duplexing two RAID 0 arrays. This yields the fault tolerance of RAID 1 and the input/output speed of RAID 0.