RFS đòi hỏi một môi trường kết nối chế độ mạch ảo, trong khi NFS chạy trong trạng thái kết nối. RFS cung cấp hỗ trợ cho tập tin bắt buộc và ghi khóa. Điều này không được định nghĩa như là một phần của giao thức NFS. NFS có thể chạy trong môi trường không đồng nhất, trong khi RFS là hạn chế trong các môi trường UNIX | Clustered and Distributed Filesystems 303 RFS requires a connection-mode virtual circuit environment while NFS runs in a connectionless state. RFS provides support for mandatory file and record locking. This is not defined as part of the NFS protocol. NFS can run in heterogeneous environments while RFS is restricted to UNIX environments and in particular System V UNIX. RFS guarantees that when files are opened in append mode O_APPEND the write is appended to the file. This is not guaranteed in NFS. In an NFS environment the administrator must know the machine name from which the filesystem is being exported. This is alleviated with RFS through use of the primary server. When reading through this list it appears that RFS has more features to offer and would therefore be a better offering in the distributed filesystem arena than NFS. However the goals of both projects differed in that RFS supported full UNIX semantics whereas for NFS the protocol was close enough for most of the environments that it was used in. The fact that NFS was widely publicized and the specification was publicly open together with the simplicity of its design and the fact that it was designed to be portable across operating systems resulted in its success and the rather quick death of RFS which was replaced by NFS in SVR4. RFS was never open to the public in the same way that NFS was. Because it was part of the UNIX operating system and required a license from AT T it stayed within the SVR3 area and had little widespread usage. It would be a surprise if there were still RFS implementations in use today. The Andrew File System AFS The Andrew Filesystem AFS MORR86 was developed in the early to mid 1980s at Carnegie Mellon University CMU as part of Project Andrew a joint project between CMU and IBM to develop an educational-based computing infrastructure. There were a number of goals for the AFS filesystem. First they required that UNIX binaries could run on clients without modification requiring
