Patent ID: 7152182

Claim:
A data redundancy system, comprising: a primary storage facility for storing a primary copy of data, the primary storage facility including; a first redundancy appliance operable in a role for receiving a sequence of write requests and for storing data for the sequence of write requests in storage associated with the primary storage facility; and a second redundancy appliance for shadowing the first redundancy appliance wherein the second redundancy appliance assumes the role of the first redundancy appliance; a secondary storage facility for storing data that is redundant of the primary copy of the data, the secondary storage facility discrete from the primary storage facility and including; a third redundancy appliance operable in a role for storing redundant data for the sequence of write requests in storage associated with the secondary facility; and a fourth redundancy appliance for shadowing the third redundancy appliance wherein the fourth redundancy appliance assumes the role of the third redundancy appliance in the event of a fault at the third redundancy appliance.