A file storage system for storing data of a file received from a client includes a back-end file server in which the data is stored. The system includes a cache appliance in communication with the file server, such that the appliance stores portions of the data or attributes of the file, and uses the stored data or attributes to process file system requests received from the client, and which reads and writes data and attributes to the back-end file server independently. A system for responding to a file system protocol request in regard to a back-end server includes a token server. The system includes 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, and reading and writing data and attributes to the back-end servers when tokens are revoked, the cache appliance having persistent storage in which data are stored, and the token server having persistent storage in which tokens are stored. A storage system includes a plurality of backend servers. The system includes a token server which grants permission to read and write file attributes and data system, and includes a plurality of cache appliances in communication with at least one of the backend servers and the token server for processing an incoming NFS request to the one backend server. Each cache appliance comprises an NFS server which converts incoming NFS requests into cache manager operations; a token client module in communication with the token server having a cache of tokens obtained from the token server; a cache manager that caches data and attributes and uses tokens from the token client module to ensure that the cached data or attributes are the most recent data or attributes, and an NFS client which sends outgoing NFS requests to the back-end file server. Methods for storing data of a file received from a client.