level 1

1) in referring to a multimedia PC, one equipped for the initial Microsoft Multimedia PC (MPC) specifications; 2) as applied to a videodisc system, the common industry designation for one that supports only direct controls such as start and stop, rather than complete computer-controlled interaction or programmability

Complete mirror system--two sets of disks both reading and writing the
same data. This has the benefits of level 0 plus the security of full redundancy--but at
twice the cost. Some performance advantage can be gained in read because only
one copy need be read, so two reads can occur simultaneously.