Highly available asynchronous I/O for clustered computer systems

摘要

One embodiment of the present invention provides a system that allows an I/O request to proceed when a primary server that is processing the I/O request fails, and a secondary server takes over for the primary server. Upon receiving an I/O request from an application running on a client, the system stores parameters for the I/O request on the client, and sends the I/O request to the primary server. Next, the system allows the application on the client to continue executing while the I/O request is being processed. If the primary server fails after the I/O request is sent to the primary server, but before an I/O request completion indicator returns from the primary server, the system retries the I/O request to the secondary server using the parameters stored on the client. The I/O request may originate from a number of different sources, including a file system access, an I/O request from a database system, and a paging request from a virtual memory system. In a variation on the above embodiment, the act of storing the parameters for the I/O request on the client includes creating a distributed object defined within a distributed object-oriented programming environment, and sending a reference to the distributed object to the primary server to be stored on the primary server. This causes a distributed operating system to keep track of the reference so that if the primary server fails, the reference count on the distributed object drops to zero and the distributed operating system notifies the client that the distributed object is unreferenced. This allows the client to deduce that the primary server has failed.