Patent ID: 6671821
Filing Date: 2003-12-30
Classification: G06F

Abstract:
A method for fault tolerant operation of a distributed server system that includes N asynchronous servers that may experience faults, comprising:receiving a series of requests from a client over a time interval associated with the requests; at each of the N servers, processing some or all of the client requests including, for each of the requests processed at a server, updating a state of a state machine at that server according to the request and transmitting a response to the client; and resetting each of the N servers repeatedly during the time interval, wherein resetting a server includes establishing the state of the state machine at that server using data stored at other of the servers so that the state at that server corresponds to a common state of the server system; wherein when (a) for a predetermined duration time window, fewer than N/3 of the server systems experience faults in any time window of the time interval of the requests of that predetermined duration, and (b) N/3 or more of the N servers experience faults at some time during the time interval of the requests, the N servers provide responses to the client that are sufficient for the client to determine correct responses to each of the series of requests.