Clustering the Existing (Working) Portal

Hi,

We are working on EP 5.0 with huge content (stand alone instance) and planning to upgrade to EP 6.0.But it is getting delayed (post phoned) to another 10 months and the problem is the users are getting increased. Present users of the portal are over 20,000.

Is there any possibility to add another instance Portal cluster (Load balancing) to the Exiting Portal server at this stage. If so what is the procedure for that.

Help can be appreciated (it becomes a critical issue to us).

Thanks in advance,

Sudhir