Patent ID: 7577867

Claim:
A system for consistent data recovery, comprising a storage area network (SAN) of initiator nodes and target nodes, wherein initiator nodes issue I/O requests and target nodes respond to I/O requests, the SAN being represented logically as a plurality of consistency groups of nodes, G 1 , . . . , Gn, each consistency group representing: (A) at least one logical storage unit (LU), each LU acting as a target node within the SAN; (B) at least one host device, each host device acting as an initiator within the SAN, each host device comprising (B.1) a transmitter for issuing I/O requests to at least one LU, and each host device being associated with (C) a host device agent, the host device agent comprising: (C.1) an interceptor for intercepting I/O requests issued by the host device and performing one or more of sending the intercepted I/O requests to the at least one LU, redirecting the intercepted I/O request to another LU, splitting the intercepted I/O requests to enable sending of the intercepted I/O requests first to a data protection agent prior to transmission to the at least one LU; and (C.2) a router for forwarding the intercepted I/O requests to the data protection appliance; (D) a data protection appliance (DPA) acting as both an initiator node and a target node within the SAN, the DPA comprising: (D.1) a receiver for receiving a current I/O request forwarded by an agent router for a host device; (D.2) a router for forwarding the current I/O request to a replication facility; (D.3) an ACK transmitter for sending an acknowledgement for an I/O request to an agent, wherein said agent router is operable to halt forwarding further host device I/O requests until the acknowledgement for a current I/O request is received from the DPA, and to resume forwarding after the acknowledgement for the current I/O request is received; and (D.4) a tag initiator for issuing an instruction for the replication facility to tag a consistency group at a current point in time; and (E) a replication facility comprising: (E.1) a receiver for receiving I/O requests forwarded by said DPA router; and (E.2) a data recoverer for restoring the LUs to a tagged state, based on I/O requests received by said DPA receiver, the system further comprising (F) a DPA manager operable to send requests to said DPAs of G 1 , . . . , Gn, (r 1 ) to stop their ACK transmitters sending acknowledgements for I/O requests to said host device agents of G 1 , . . . , Gn, and (r 2 ) to tag G 1 , . . . , Gn.