The zfs send command creates a stream representation of a snapshot that is written to standard output. By default, a full stream is generated. You can redirect the output to a file or to a different system. The zfs receive command creates a snapshot whose contents are specified in the stream that is provided on standard input. If a full stream is received, a new file system is created as well. You can send ZFS snapshot data and receive ZFS snapshot data and file systems with these commands. See the examples in the next section.

Au final on peut faire une copie de snapshot comme ceci :
zfs send -i mainVolume/mainDataSet@snapshotSource mainVolume/mainDataSet@snapshotTarget |zfs recv backupDisk/mainDataSet

--> Bien entendu, le snapshot source doit également exister sur le disque de backup.