1. An apparatus, comprising: a local storage system having a local volume with a plurality of local regions, and a first processor configured to compute respective local signatures over the local regions, and to create a local bitmap having local bitmap entries, each local bitmap entry indicating a local realization status for an associated local region in a current snapshot, wherein the local realization status is one of a realized status or an unrealized status; and a remote storage system having a remote volume with remote regions in a one-to-one correspondence with the local regions, and a second processor configured to lock the remote volume to a read-only mode to prevent updates to the remote volume prior to a synchronization of the local volume and the remote volume, to create a remote bitmap having remote bitmap entries, each remote bitmap entry indicating a remote realization status for an associated remote region, wherein the remote realization status is one of a realized status or an unrealized status, to compute respective remote signatures over the remote regions, to identify for a given remote region having a given remote signature and a corresponding local region having a given local signature that the given remote signature does not match the given local signature, and to replace data in the given remote region with data from the corresponding local region, wherein: the second processor is further configured to determine whether the local realization status of a corresponding local region and the remote realization status of a corresponding remote region to the corresponding local region are both the realized status and if so, to transmit a request to compute the respective local signatures over the corresponding local region, the first processor is further configured to receive parameters relating to the corresponding local region and to compute the respective local signatures over the corresponding local region having the corresponding local realization status and to send the respective local signatures to the second processor, and the second processor is further configured, in response to receiving the respective local signatures, to compute the corresponding remote signatures over the corresponding remote region having the corresponding remote realization status.