If clustered properly, using the Network Deployment Manager, and proper WebSphere clustering, then your WebSphere Portal nodes, which will handle client requests, will all share a common, centralized, portal configuration database (WPS). They will also all point to the same database for member management information (WMM). They will also read from a common WebSphere configuration repository which will be managed by the deployment manager.
Deploying a portlet will result in the configuration being written to the centralized database, and the binaries pushed out to all nodes in the cluster, so all nodes will be serving the same content to the end user.
At least, that's the way it's supposed to work.
Clustering is always a challenge.
Test, test, test to ensure your setup is working properly.
Good luck!
-Cameron McKenzie
