An efficient scheme for providing high availability

Replication at the partition level is a promising approach for increasing availability in a Shared Nothing architecture. We propose an algorithm for maintaining replicas with little overhead during normal failure-free processing. Our mechanism updates the secondary replica in an asynchronous manner: entire dirty pages are sent to the secondary at some time before they are discarded from primary's buffer. A log server node (hardened against failures) maintains the log for each node. If a primary node fails, the secondary fetches the log from the log server, applied it to its replica, and brings itself to the primary's last transaction-consistent state. We study the performance of various policies for sending pages to secondary and the corresponding trade-offs between recovery time and overhead during failure-free processing.