We on Openstack infrastructor team use Jenkins extensively. Our jenkins servers, at peak load, runs 4000+ jobs per day. At that load we are running up to the limit that a single Jenkins master can support. We wanted to balance the load across multiple masters, however Jenkins core does not support multiple masters. The gearman-plugin will provide some load balancing and redundancy to any Jenkins deployment.
Jenkins core does not support multiple masters. You can setup multiple Jenkins masters but there is no coordination between them.