Patent ID: 9323681
Filing Date: 2016-04-26
CPC Classification: G06F

Claim Text:
1. A system for responding to a file system protocol request in regard to a back-end server comprising: a primary token server; a plurality of cache appliances in communication with the token server, each of which receives tokens from the token server to synchronize access to data and attributes caches of the cache appliances by revoking incompatible tokens when granting new tokens, and reading and writing data and attributes to the back-end server when tokens are revoked, the cache appliance having persistent storage in which data and attributes are stored, and the token server having persistent storage in which tokens are stored and where the cache appliance maintains its own copy of modified data and attributes, and stores them to the back-end file server upon revocation of a write token, wherein the token server produces a write data token to write data to the back-end server by the cache appliance, and ensures that no two write data tokens are granted over a single byte of any same file, wherein the token server produces write attribute tokens for files stored in the back-end server and ensures that no two write attribute tokens are granted for the same file, and wherein the token server revokes an already granted write data or write attribute token by recalling the granted write data or write attribute token if a new write data or write attribute token is requested from the token server and is incompatible with the already granted write attribute or write data token and when a write data or write attribute token is revoked, the cache appliance writes the modified version of the file's data or attributes to the back-end file server; and a hot spare token server to which the write data tokens and write attribute tokens are mirrored, the hot spare token server replaces the primary token server if the primary token server fails and continues operation with a reconstructed token database, if the hot spare token server replaces the primary token server, the hot spare server becomes the primary token server and each write data token and write attribute token that is mirrored in the hot spare token server is revoked in a same way as when a corresponding write data token or read data token is revoked in the primary token server, the token server produces hold modified tokens for the cache appliance for the file's attributes and data, and data and attributes associated with the hold modified tokens are retrieved directly from the cache appliance having the hold modified tokens, the hold modified tokens identify the cache appliance having the hold modified tokens.