At the NSD Node, I issue the command

# mmaddnode -N node1
Thu Jul 23 13:40:12 SGT 2015: mmaddnode: Processing node node1
mmaddnode: Node node1 was not added to the cluster.
The node appears to already belong to a GPFS cluster.
mmaddnode: mmaddnode quitting.  None of the specified nodes are valid.
mmaddnode: Command failed.  Examine previous error messages to determine cause.

If we do a mmcluster, the node is not around in the cluster

# mmcluster |grep node1

If the node is not in the cluster, issue this command on the client node that could not be added:

# mmdelnode -f
mmdelnode: All GPFS configuration files on node goldsvr1 have been removed.

Reissue the mmaddnode command. References:

1. Node cannot be added to the GPFS cluster