US Patent 7640582 Clustered filesystem for mix of trusted and untrusted nodes

A cluster of computer system nodes share direct read/write access to storage devices via a storage area network using a cluster filesystem. At least one trusted metadata server assigns a mandatory access control label as an extended attribute of each filesystem object regardless of whether required by a client node accessing the filesystem object. The mandatory access control label indicates the sensitivity and integrity of the filesystem object and is used by the trusted metadata server(s) to control access to the filesystem object by all client nodes.