RAID 1[edit]
See also: RAID 1E
Diagram of a RAID 1 setup
RAID 1 consists of an exact copy (or mirror) of a set of data on two or more disks; a classic RAID 1 mirrored pair contains two disks. This layout is useful when read performance or reliability is more important than the resulting data storage capacity; such an array can only be as big as the smallest member disk.[5][6]
Depending on the nature of I/O load, random read performance of a RAID 1 array may equal up to the sum of each member's performance,[a] while the write performance remains at the level of a single disk.[b][6][7]