Method and apparatus for transactional fault tolerance in a client-server system

A fault tolerant system, comprising:

• a primary server configured to execute a service for a plurality of clients;
• a secondary server configured to execute the service;
• checkpoint engines implemented in the primary server and the secondary server, the checkpoint engines configured to establish a copy of an execution context of the primary server on the secondary server at each of a plurality of checkpoints, buffer output data generated by the primary server between successive ones of the plurality of checkpoints, and release buffered output data in response to establishment of the copy of the execution context at each of the plurality of checkpoints.