Fault tolerant computer system with provision for handling external events
First Claim
1. In a fault tolerant computer system including a data processor providing at least one task which performs a persistent action and wherein said task is subject to receiving one or more external signals whose time of occurrence may affect the performance of said task, a method comprising:
- providing a backup task external to said data processor for backing up said one task,transmitting messages to said one task;
storing messages transmitted to said one task;
also storing external event data indicative of each external event type and its occurrence relationship to a predetermined primary task event;
transmitting at least certain ones of the stored messages to said backup task subsequently to said storing messages in a manner such that at least those particular messages which have been processed by said one task are transmitted to said backup task prior to performance of said persistent action;
also transmitting said external event data and said occurrence relationship to said backup task prior to performance of said persistent action;
said one task continuing to process messages transmitted thereto so long as the aforementioned transmitting of messages and external event data to said backup task is met; and
in the event of failure of said one task, causing said backup task to process said messages transmitted thereto while using said external event data and said occurrence relationship transmitted thereto to redeliver each external signal to said backup task at a time such that said backup task will properly recover.
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Accused Products
Abstract
A fault tolerant computer system employing primary tasks and corresponding backup tasks. The system operates to provide fault tolerant operation even where uncontrolled external events may occur whose time of occurrence may affect task performance. For this purpose, external event data is stored for each external event occurring during performance of a primary task which indicates the event type and the relationship between the occurrence of the external event and the occurrence of a predetermined primary task event, such as a memory access operation. This external event data is sent to each respective backup task along with messages transmitted to the respective primary task. In the event a primary task fails, the backup task will replay the failed primary task by processing these transmitted messages while using the transmitted external event data to redeliver each external signal to the backup task at an appropriate time which will assure that the backup task properly recovers the primary task.
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Citations
24 Claims
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1. In a fault tolerant computer system including a data processor providing at least one task which performs a persistent action and wherein said task is subject to receiving one or more external signals whose time of occurrence may affect the performance of said task, a method comprising:
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providing a backup task external to said data processor for backing up said one task, transmitting messages to said one task; storing messages transmitted to said one task; also storing external event data indicative of each external event type and its occurrence relationship to a predetermined primary task event; transmitting at least certain ones of the stored messages to said backup task subsequently to said storing messages in a manner such that at least those particular messages which have been processed by said one task are transmitted to said backup task prior to performance of said persistent action; also transmitting said external event data and said occurrence relationship to said backup task prior to performance of said persistent action; said one task continuing to process messages transmitted thereto so long as the aforementioned transmitting of messages and external event data to said backup task is met; and in the event of failure of said one task, causing said backup task to process said messages transmitted thereto while using said external event data and said occurrence relationship transmitted thereto to redeliver each external signal to said backup task at a time such that said backup task will properly recover. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 18, 19, 20)
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11. In a fault tolerant computer system including a data processor providing a plurality of primary tasks, at least one of said primary tasks performing a persistent action, and wherein each primary task is subject to receiving one or more external signals whose time of occurrence may affect the performance of its respective task, a method comprising:
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providing a corresponding plurality of interconnected backup tasks external to said data processor for backing up said plurality of primary tasks; transmitting messages between said primary tasks for processing thereby; storing the transmitted messages; also storing external event data indicative of each external event type and its occurrence relationship to a predetermined primary task event; each primary task processing the messages transmitted thereto; transmitting at least particular ones of the stored messages to said backup tasks subsequently to said storing messages in a manner such that there is transmitted to said backup tasks, prior to the performance of a persistent action, at least those messages required for said backup tasks to recover from a failure of said data processor; also transmitting said external event data and said occurrence relationship to respective backup tasks prior to performance of said persistent action; said primary tasks continuing to process messages transmitted thereto so long as the aforementioned transmitting of messages and external event data to said backup tasks is met; and recovering from said failure by causing said backup tasks to process the messages and external event data transmitted thereto, each occurrence relationship being used during said recovering to determine when its respective external event is to occur, whereby proper recovery is achieved. - View Dependent Claims (12, 13, 14, 15, 16, 17, 21, 22, 23, 24)
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Specification