why ?  You don't have SyncIQ ?  If you don't have SyncIQ you could use rsync/scp to copy data between the clusters. Or you could use a "proxy" windows systems that will map CIFS shares from both clusters and then use robocopy/emcopy to copy the data.
Hey Isilon Support Community,  Can you mount CIFS shares between Isilons?  If so can you help out with syntax, because I seem to be having an issue doing so.   Thank you,
CIFS mounting