Patent ID: 7376859

Claim:
A method comprising: receiving an I/O command at a switch from a host; if the I/O command is a write I/O, then writing data via the switch to a primary storage subsystem and a secondary storage subsystem, wherein the switch couples the host to the primary storage subsystem and the secondary storage subsystem, and wherein the data written to the primary storage subsystem and the data written to the secondary storage subsystem are the same; receiving an indication of a failure of the primary storage subsystem at the switch; and subsequently, directing a command from the host received at the switch to the secondary storage subsystem for completion by changing a source volume and a target volume in the command to correspond to volumes in the secondary storage subsystem, wherein the source volume and the target volume are for I/O operations, and wherein the changing is performed by a switching application in the switch, wherein a hardware unit is coupled to the primary storage subsystem, wherein the hardware unit traps alerts related to I/O failures and notifies the switch to perform the changing, and wherein in response to the hardware unit receiving a notification that the primary storage subsystem is fixed creating a copy of secondary storage subsystem data to guard against any subsequent failure during resynchronization of the primary and secondary storage systems.