A system comprising: a first storage array, wherein the first storage array comprises one or more storage devices; a second storage array, wherein the second storage array comprises one or more storage devices; wherein responsive to detecting a request to replicate a first volume from the first storage array to the second storage array, the first storage array is configured to: identify a first medium corresponding to a first snapshot of the first volume, wherein the first medium includes one or more regions; make a policy decision and notify the second storage array that the first medium is to be replicated; request and receive, from the second storage array, a first list of a plurality of regions stored on the second storage array, identified by the second storage array, which correspond to mediums that originated on the first storage array; for each region of the first medium: use the first list to determine whether the region is already stored on the second storage array prior to detecting the request to replicate the first volume; send a first reference to the second storage array responsive to determining the region is already stored on the second storage array prior to detecting the request to replicate the first volume, wherein the first reference identifies an existing region on the second storage array; and send a second reference to the second storage array responsive to determining the region is a duplicate of a second region of the first medium, wherein the second reference identifies the second region. a first storage array, wherein the first storage array comprises one or more storage devices; a second storage array, wherein the second storage array comprises one or more storage devices; wherein responsive to detecting a request to replicate a first volume from the first storage array to the second storage array, the first storage array is configured to: identify a first medium corresponding to a first snapshot of the first volume, wherein the first medium includes one or more regions; make a policy decision and notify the second storage array that the first medium is to be replicated; request and receive, from the second storage array, a first list of a plurality of regions stored on the second storage array, identified by the second storage array, which correspond to mediums that originated on the first storage array; for each region of the first medium: use the first list to determine whether the region is already stored on the second storage array prior to detecting the request to replicate the first volume; send a first reference to the second storage array responsive to determining the region is already stored on the second storage array prior to detecting the request to replicate the first volume, wherein the first reference identifies an existing region on the second storage array; and send a second reference to the second storage array responsive to determining the region is a duplicate of a second region of the first medium, wherein the second reference identifies the second region. identify a first medium corresponding to a first snapshot of the first volume, wherein the first medium includes one or more regions; make a policy decision and notify the second storage array that the first medium is to be replicated; request and receive, from the second storage array, a first list of a plurality of regions stored on the second storage array, identified by the second storage array, which correspond to mediums that originated on the first storage array; for each region of the first medium: use the first list to determine whether the region is already stored on the second storage array prior to detecting the request to replicate the first volume; send a first reference to the second storage array responsive to determining the region is already stored on the second storage array prior to detecting the request to replicate the first volume, wherein the first reference identifies an existing region on the second storage array; and send a second reference to the second storage array responsive to determining the region is a duplicate of a second region of the first medium, wherein the second reference identifies the second region. use the first list to determine whether the region is already stored on the second storage array prior to detecting the request to replicate the first volume; send a first reference to the second storage array responsive to determining the region is already stored on the second storage array prior to detecting the request to replicate the first volume, wherein the first reference identifies an existing region on the second storage array; and send a second reference to the second storage array responsive to determining the region is a duplicate of a second region of the first medium, wherein the second reference identifies the second region.