Patent ID: 7660955

Claim:
A method of creating a consistency group, comprising: transferring segments of data identified in a first data structure, from a source of a plurality of sources to a destination of a plurality of destinations; updating said first data structure to indicate a transfer of a segment of data; and in a first mode of operation: updating said first data structure to indicate additional segments of data to be transferred between the sources and destinations; polling a plurality of sources to determine a backlog of each polled source and an estimated drain time for each determined backlog; and comparing an estimated drain time to a predetermined drain time limit; as a function of said comparison, selectively switching from said first mode to a second mode of operation; wherein said second mode includes: forming a consistency group; and updating a second data structure instead of said first data structure to indicate additional segments of data to be transferred between the source and destination of a consistency group being formed; upon successful formation of a consistency group in said second mode, switching operations from said second mode to a third mode of operation; wherein said third mode includes: updating said first data structure to indicate additional segments of data to be transferred between the sources and destinations; wherein said third mode further comprises determining to form a consistency group; and switching operations from said third mode to a fourth mode of operation; wherein said fourth mode includes: forming a consistency group; updating a second data structure instead of said first data structure to indicate additional segments of data to be transferred between the source and destination of a consistency group being formed; upon expiration of a maximum consistency group drain time limit, switching operations from said fourth mode of operation to said first mode of operation to resume polling of said sources; and upon successful formation of a consistency group in said fourth mode, switching operations from said fourth mode to said third mode of operation.