Presentation on theme: "Andrew File System CSS534 ZACH MA. History Originated in October 1982, by the Information Technology Center (ITC) formed with Carnegie Mellon and IBM."— Presentation transcript:
Andrew File System CSS534 ZACH MA
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.
General Goals High availability Ease of expansion Incorporation of new technologies Good performance even during peak periods With graceful response to overload
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
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.
Server Processes File Server Basic OverSeer Server(BOS Server) Protection Server Volume Server Volume Location Server(VL Server) Salvager Update Server Backup Server
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
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
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
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.
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
VL Server Interaction
Password and Mutual Authentication
Updating Copies of Cached Files X X ->Y ->Z
Summary Pros: Scalability Security Reliability Availability Cons: Authentication may cause problems Conflicts with UNIX file semantics
References  Howard, John H. An overview of the andrew file system. Carnegie Mellon University, Information Technology Center,  Administrator Guide,  User Guide,