Abstract: A storage system that accomplishes both robustness and scalability. The storage system includes replicated region servers configured to handle computation involving blocks of data in a region. The storage system further includes storage nodes configured to store the blocks of data in the region, where each of the replicated region servers is associated with a particular storage node of the storage nodes. Each storage node is configured to validate that all of the replicated region servers are unanimous in updating the blocks of data in the region prior to updating the blocks of data in the region. In this manner, the storage system provides end-to-end correctness guarantees for read operations, strict ordering guarantees for write operations, and strong durability and availability guarantees despite a wide range of server failures (including memory corruptions, disk corruptions, etc.) and scales these guarantees to thousands of machines and tens of thousands of disks.