numCacheNodes
The initial number of cache nodes that the cluster has.
For clusters running Redis, this value must be 1. For clusters running Memcached, this value must be between 1 and 40.
If you need more than 40 nodes for your Memcached cluster, please fill out the ElastiCache Limit Increase Request form at http://aws.amazon.com/contact-us/elasticache-node-limit-request/.