RAID 1

For Highest performance, the controller must be able to perform two concurrent separate Reads per mirrored pair or two duplicate Writes per mirrored pair.

RAID Level 1 requires a minimum of 2 drives to implement

One Write or two Reads possible per mirrored pair

Twice the Read transaction rate of single disks, same Write transaction rate as single disks

100% redundancy of data means no rebuild is necessary in case of a disk failure, just a copy to the replacement disk

Transfer rate per block is equal to that of a single disk

Under certain circumstances, RAID 1 can sustain multiple simultaneous drive failures

Simplest RAID storage subsystem design

Highest disk overhead of all RAID types (100%) - inefficient

Typically the RAID function is
done by system software, loading the CPU/Server and possibly degrading
throughput at high activity levels. Hardware implementation is strongly
recommended

May not support hot swap of failed disk when implemented in "software"