If you do not need snapshots then maybe vol copy will do what you need.
vol copy can copy snapshots as well. From 7.2.6.1 vol man page,
vol copy start [ -S | -s snapshot ] source destination
Copies all data, including snapshots, from one vol- ume to another. If the -S flag is used, the com- mand copies all snapshots in the source volume to the destination volume. To specify a particular snapshot to copy, use the -s flag followed by the name of the snapshot.
Though I'm not sure this would be any faster than a snapmirror.
Andre, I'd be interested to hear what your outcome of this eventually is.
Thanks,