Bandwidth consumption between a data replication source and destination and storage consumption at the destination are reduced, when logical block mirroring is used with source deduplication, by eliminating repeated transmission of data blocks from source to destination. A reference is created for each data block at the source, the reference being unique within a storage aggregate of the source. During a mirror update, the source initially sends only the references of modified data blocks to the destination. The destination compares those references against a data structure to determine whether the destination already has any of those data blocks stored. If the destination determines that it already has a data block stored, it does not request or receive that data block again from the source. Only if the destination determines that it has not yet received the referenced data block does it request and receive that data block from the source.