The RAID device will not fail so long as any one of the partitions remains usable. The performance of the RAID device does not decrease substantially when operating in a degraded mode. Low hardware cost. RAID mirrors typically consist of only two disk drives. This makes RAID 1 a good choice where limitations on the number of disks exist.
Mirrors are the easiest RAID configuration to setup and maintain.
Since each partition is a mirror of the others, that disk space cannot be used to store additional data. RAID 5 is a more efficient use of disk space. Several equally sized partitions are combined to form one logical device. Data and parity information is dispersed among the available partitions. Parity data is divided equally among the partitions.