What I do is to backup using the virtual ip.
Say you have two nodes, nodea-myserver and nodeb-myserver and the virtual IP name is clus-myserver.
Set up the backup specification for clus-myserver including only the relevant filesystems. Exclude those filesystems from the nodea-myserver and nodeb-myserver backups.
There is a section in the help on cluster-aware clients.
HTH
Jeremy