How fast can you set up a demo cluster:
Once your two instances are up and running, I literally followed the Riak documentation at Basic Cluster Setup. It was really that easy. The was one gotcha, though. Make sure that when you choose the IP address to bind (and name) for the nodes in your cluster that you use the EC2 Private IP Address (or DNS name should be fine too.)
If you’re looking something bigger check this script for launching a 100-node Riak cluster.
Original title and link: Setting Up a 3 Node Riak Cluster With EC2 Cluster Compute Instances (NoSQL databases © myNoSQL)