Sorry, not mbuff but mbuffer. It just adding a memory buffer between STDIN and STDOUT. Useful to smooth data flow, so reading from disk do not need to wait for SSH to transmit and other way around. In you case it cold be something like that. ( I'm writing command from memory, do not use it unless checked)

dd if=/dev/sda bs=16M | mbuffer -s 128k -m 2G -o - | ssh remoteuser@remote.host.com dd of=/storage/backup.img