Patent ID: 7571268

Claim:
A method, comprising: sending, by a primary control unit, a selected time to a plurality of secondary control units; periodically synchronizing clocks at the primary control unit and the secondary control units with a time server; and consistently updating, by the primary control unit and the plurality of secondary control units, secondary storage subsystems coupled to the plurality of secondary control units at the selected time, wherein the method further comprises: (i) determining, by the primary control unit, whether each of the plurality of secondary control units has initiated a process for consistently updating the secondary storage subsystems coupled to the plurality of secondary control units at the selected time; and (ii) requesting, by the primary control unit, each of the plurality of secondary control units to complete the process for consistently updating the secondary storage subsystems, in response to determining by the primary control unit that each of the plurality of secondary control units has initiated the process for consistently updating the secondary storage subsystems coupled to the plurality of secondary control units at the selected time.