1. Andrew File System CSS534 ZACH MA

2. History  Originated in October 1982, by the Information Technology Center (ITC) formed with Carnegie Mellon and IBM Corporation  Commercialized by Transarc Corporation in 1989 and then made into an IBM product that was extensively used in the 1990s.  Made open-source by IBM under the name OpenAFS in 2000, and continues to be in widespread use at Carnegie Mellon and many other institutions.

3. General Goals  High availability  Ease of expansion  Incorporation of new technologies  Good performance even during peak periods  With graceful response to overload

4. Design Choices  Make the file system compatible with UNIX at the system call level  Use whole files as the basic unit of data movement and storage, rather than some smaller unit such as physical or logical records  Implement it with many relatively small servers rather than a single large machine

5. Servers and Clients  Two basic classes of machines  File server machines  Client machines  File server machines provide file storage and delivery service, along with other specialized services, to the other subset of machines in the network, the client machines  There are generally many more client workstations than file server machines.

6. Server Processes  File Server  Basic OverSeer Server(BOS Server)  Protection Server  Volume Server  Volume Location Server(VL Server)  Salvager  Update Server  Backup Server

7. File Server  Delivering and storing files  Maintaining the hierarchical directory structure  Handling all types of file requests  Keeping track of status information  Validating user identity  Creating symbolic and hard links between files

8. Basic OverSeer Server(BOS Server)  Constant monitoring on the other server processes  Automatic incident response  Interacting with system administrator  Helps system administrators to manage system configuration information

9. Client Processes – Cache Manager  Only component that resides on client machines  Main duty is to translate file requests (made by application programs on client machines) into remote procedure calls (RPCs) to the File Server.  Cache files before passing data on to the application program  Track the state of files

10. Cells and Volumes  Cell  A cell is an administratively independent site running AFS.  Volume  A unit of disk space that functions like a container for a set of related files, keeping them all together on one partition.  Can vary in size, but smaller than a partition.

11. Other Parts Required  Kerberos KDC (Key Distribution Center)  Performs two main functions related to network security V erifying the identity of users Providing methods to achieve mutual authentication  Network Time Protocol Daemon(NTPD)  Guarantee that all of the file server machines and client machines agree on the time

12. VL Server Interaction

13. Password and Mutual Authentication

14. Updating Copies of Cached Files X X ->Y ->Z

15. Summary  Pros:  Scalability  Security  Reliability  Availability  Cons:  Authentication may cause problems  Conflicts with UNIX file semantics

16. References [1] Howard, John H. An overview of the andrew file system. Carnegie Mellon University, Information Technology Center, 1988. [2] Administrator Guide, http://docs.openafs.org/index.html [3] User Guide, http://docs.openafs.org/index.html [4] http://en.wikipedia.org/wiki/Andrew_File_System [6] http://www.cmu.edu/corporate/news/2007/features/andrew/history_overview.shtml