Controlling Data Lag in a Replicated Computer System

摘要

A method and system is provided for measuring, guaranteeing, and reducing replication data lag time between a primary system and one or more standby systems. Each standby system determines the lag time between the generation of a consistent version of data on the primary system and the time that the consistent version is applied on the standby system. Applications can request and be guaranteed to receive data from a standby system that is identical to the state on the primary system at the time of the query, or lag the primary state only by a maximum tolerable amount. A standby system may also publish a service that guarantees a maximum lag time and withdraw the service offer when the actual lag time exceeds the guaranteed lag time. Implications for implementing synchronous and asynchronous replication as well as performance optimizations are also discussed.