Clustering the GroupWise Web applications (WebAccess, Calendar Publishing Host, and Monitor) is not currently supported.
Because the GroupWise Web applications are installed into your Web server, clustering the GroupWise Web applications would entail clustering your entire Web server. If you are already successfully clustering your Web server, you should be able to install the GroupWise Web applications into that clustered Web server in the same way that you have installed other Web applications into your clustered Web server. However, you cannot receive support to set up this configuration of the GroupWise Web applications. For guidance, refer to the WebAccess Application (Web Server)
section in a helpful GroupWise 8 Cool Solutions article. The principles are the same for GroupWise 8 and GroupWise 2012.