Patent ID: 8190838

Claim:
A system, comprising: a data replication system comprising a plurality of data replication nodes; each data replication node comprising a durable storage, wherein, in response to receiving a write request from a client, the data replication system is configured to perform a synchronous replicate data write of the data for the write request to each of a set of the plurality of data replication nodes and to perform an asynchronous replicate data write of the data for the write request to each of the plurality of data replication nodes not in the set, wherein the data replication system is configured to change a number of nodes in the set of the plurality of data replication nodes and a number of the data replication nodes not in the set between a configuration and another configuration, wherein the set includes, in both the configuration and the another configuration, at least one of the plurality of data replication nodes but fewer than all the plurality of data replication nodes, and wherein the nodes not in the set include, in both the configuration and the other configuration, at least one of the plurality of data replication nodes but fewer than all the plurality of data replication nodes; wherein the data replication system is configured to send a write completion acknowledgement to the client once each synchronous replicate data write has been completed in the durable storage in each respective node of the set regardless of whether each asynchronous replicate data write has yet been completed in the durable storage in each respective node not in the set.