There is a master node for CVM as well as a primary for SFCFS. When growing a file system, you grow the volume from the CVM master, and then grow the file system from any SFCFS node. The CVM master and the SFCFS node can be different nodes.
To determine the primary file system in a cluster
fsclustadm -v showprimary
To determine that the current node is the master CVM node
vxdctl -c mode
To actually increase the size of the file system
fsadm -F vxfs -b