Cloud computing has been adapted for various application domains including industrial automation systems. Migrating industrial automation systems to a public cloud would deliver several advantages such as cost reduction for system developers and users. However the availability current industrial automation systems require is higher than the availability guaranteed by IaaS providers. To close the availability gap, we propose a reliable cloud-based feedback control system. The proposed system achieves high availability of feedback controllers by using multiple regions and peer-to-peer communication for controller status sharing. We have developed a prototype system based on Amazon EC2. The developed system shows that the feedback controllers can perform failover for two types of failures, namely, network failure and controller failure.