Fault tolerance using logical checkpointing in computing systems

A service operating on a computer system to process requests from client processes, comprising:

• a primary service instance operating on the computer system, including means for receiving and processing client requests from the client processes;
• at least one backup service instance operating on the computer system, including means for receiving and processing the client requests, wherein each backup service instance is logically equivalent to the primary service instance;
• wherein the primary service instance includes
• means for determining which external requests, when processed by the secondary service instance, are logical requests such that processing of the determined logical requests cause the external view of each backup service instance to change;
• and
• means for communicating with each backup service instance to provide an indication of the determined logical requests to each backup service instance.

A method of operating a computer system to process requests from client processes, comprising:

• operating a primary service instance on the computer system, including receiving and processing client requests, from the client processes;
• operating at least one backup service instance on the computer system, including receiving and processing the client requests, wherein each backup service instance is logically equivalent to the primary service instance;
• wherein the step of operating the primary service instance includes
• determining which external requests, when processed by the secondary service instance, are logical requests such that processing of the determined logical requests cause the external view of each backup service instance to change;
• and
• communicating with each backup service instance to provide an indication of the determined logical requests to each backup service instance.

A method of operating a service on a computer system to process requests from client processes, comprising:

• operating a primary service instance on the computer system, including receiving and processing client requests from the client processes;
• operating at least one backup service instance on the computer system, including receiving and processing the client requests, wherein each backup service instance is logically equivalent to the primary service instance;
• wherein the step of operating the primary service instance includes
• determining which external requests, when processed by the secondary service instance, are logical requests such that processing of the determined logical requests cause the external view of each backup service instance to change;
• and
• communicating with each backup service instance to provide an indication of the determined logical requests to each backup service instance.

A program storage device readable by a machine tangibly embodying a program of instructions executable by the machine to perform method steps for operating a computer system to process requests from client processes, said method steps comprising:

• operating a primary service instance on the computer system, including receiving and processing client requests, from the client processes;
• operating at least one backup service instance on the computer system, including receiving and processing the client requests, wherein each backup service instance is logically equivalent to the primary service instance;
• wherein the step of operating the primary service instance includes
• determining which external requests, when processed by the secondary service instance, are logical requests such that processing of the determined logical requests cause the external view of each backup service instance to change;
• and
• communicating with each backup service instance to provide an indication of the determined logical requests to each backup service instance.

A program storage device readable by a machine tangibly embodying a program of instructions executable by the machine to perform method steps for operating a computer system to process requests from client processes, said method steps comprising:

• operating a primary service instance on the computer system, including receiving and processing client requests from the client processes;
• operating at least one backup service instance on the computer system, including receiving and processing the client requests, wherein each backup service instance is logically equivalent to the primary service instance;
• wherein the step of operating the primary service instance includes
• determining which external requests, when processed by the secondary service instance, are logical requests such that processing of the determined logical requests cause the external view of each backup service instance to change;
• and
• communicating with each backup service instance to provide an indication of the determined logical requests to each backup service instance.