US Patent 8214612 Ensuring consistency of replicated volumes

A method, system, and program product for ensuring consistency of dynamically changing volumes comprising creating a production change map for a first volume; wherein the production change map is marked to represent pending IO, creating a replication change map for a second volume; wherein the replication change map is marked to represent pending IO, transferring a first signature corresponding to a portion of the first volume to the replication volume, wherein the signature does not include the portion marked as pending IO in the production change map, comparing the first signature to a second signature, the second signature corresponding to a portion of the replication volume corresponding to the portion of the production volume; wherein portions marked as dirty in the replication change map are not included in the signature.