Patent ID: 6163856
Filing Date: 2000-12-19
Classification: G06F

Abstract:
A geographical data replication system comprising:a local site having at least one local server running a first file system, at least one client and first stable file storage, the local server being configured to serve via the first file system file requests from the at least one client;a remote site having at least one remote server running a second file system and second stable file storage;a network connecting the local and remote sites;the local server, being configured to intercept the file requests and to determine which of the file requests is one of a first set of file requests that will alter file state of the first file system;a log file stored on the first stable file storage in which the local server writes operations and data required to replicate changes to the file state of the first file system resulting from performing the first set of file requests, the local server being configured to periodically flush the log file to the remote site;a first identifier maintained by the first file system for each of the files on the first stable file storage, the first identifier being transmitted by the local server to the remote server for each of the flushed files;a second identifier maintained by the second file system for each of the flushed files replicated on the remote server; anda mapping table on the remote server that maintains a mapping between the first and second identifiers enabling the remote server to serve the requests from the clients;the remote server being configured to update state of the second file system in accordance with the flushed log file by performing the operations on the data represented in the flushed log file;such that, whenever failover occurs from the local to the remote server, the remote server is able to serve the requests from the clients with little or no loss of file state.