Data coherency and lock services for distributed physical file systems. Client applications are coupled to a virtual file system, which is coupled to one or more physical file systems. A lock agent is coupled to one or more lock servers and to the virtual file system. The virtual file system, in response to a file access request from a client application, submits a data validation request to the lock agent. The lock agent, in turn, submits a lease request to the lock server. When the lock server grants the lease, the lease and a validation code are returned to the lock agent. The validation code indicates whether the data in the buffer cache of the virtual file system are valid. The lock agent then returns the lease to the virtual file system, which then submits the file access request to a selected one of the physical file systems.