This paper describes current and anticipated work at the University of MichiganÕs Center for Information Technology Integration (CITI) in developing and integrating mass storage with distributed file systems, specifically with the Andrew File System (AFS).After surveying existing mass storage and associated file systems, this paper presents one approach to integrating AFS with mass storage. We consider the mass store itself to be the file system, not a bag on the side of a disk-based file system. This unifying perspective distinguishes our approach from other large-scale file systems.Instead of developing a back-end server to manage the movement of data files between traditional disk-based storage systems (employed, in our case, by AFS) and magnetic-tape or optical-based mass storage systems (of which AFS has little or no knowledge), we envision the mass store as a first-class data repository. A traditional disk-based file system serves as a (very large) cache of the mass store system. On top of that is another, large, high-speed memory cache. All storage other than the mass store is used exclusively for caching. In this approach, cache management policies are of fundamental importance.Two main requirements for this work are that the AFS name space remain unchanged, and performance seen by users must not suffer. For example, users must not have to pre-stage files explicitly in order to achieve acceptable performance.
With network security threats and vulnerabilities increasing, solutions based on online detection remain attractive. Ac omplete, durable record of all activity on a network can be used to evaluate and train intrusion detection algorithms, assist in responding to an intrusion in progress, and, if properly constructed, servea se vidence in legalp roceedings.This paper describes the Advanced Packet Vault, a technology for creating such a record by collecting and securely storing all packets observed on a network, with a scalable architecture intended to support network speeds in excess of 100 Mbps. Encryption is used to preserveusers' security and privacy,permitting selected traffic to be made available without revealing other traffic. The Va ult implementation, based on Linux and OpenBSD, is open-source.AV ault attached to a heavily loaded 100 Mbps network must capture, process, and store about a terabyte each day, so we have tob ev ery sensitive tot he recurring cost of operation and the reliability issues of 24x7 operation. We must also be sensitive tothe admissibility of information collected by the Vault in support of legalproceedings; the legalramifications of operating a vault, particularly at a public institution; and the public perception of its use.
received the BSEE and BS in computer engineering in 1977 and the MS degree in computer, information, and control engineering in 1979 from the University of Michigan. He has been employed by Bell Laboratories since 1979 and is currently on educational leave of absence to pursue the PhD degree in the Department of Electrical Engineering and Computer Science at the University of Michigan. Mr. Antonelli is a member of the Institute of Eiectrical and Electronics Engineers and a member of the Association for Computing Machinery. His research interests include the architecture of distributed systems, distributed operating systems and languages, and software engineering. RICHARD A. VOLZ is a director of the robot systems division of the Center for Robotics and Integrated Manufacturing at the University of Michigan. Prior to this, he was associate director of the University Computer Center and associate chairman of the Electrical and Computer Engineering Department. Professor Volz received his education at Northwestern University, receiving a PhD in 1964 and joined the University of Michigan that year. He has worked on computational techniques for automatic control systems and done pioneering work on computer-aided-design methods for control systems. Real-time computing systems are a more recent technical interest of his, and he has led in the design and implementation of both a real-time operating system and a higher level language for real-time control. His current research interests include software/hardware computer architectures to support robot systems s and the use of geometric models obtained from computer-aided-design systems for driving robot and sensor programming. Particular projects include (CAD) model driven vision systems, automatic determination of gripping points on objects (from CAD information), graphic programming of robots and distributed systems integration languages for r real-time control.ABSTRACT A useful tool in the development of flexible automation is a system description language which can generate a complete functional description of a manufacturing cell of arbitrary complexity. We propose a description system based on the concept of hierarchical decomposition utilizing the Ada programming language in conjunction with established diagrammatical decomposition methods. The distinguishing aspect of our work is that it takes advantage of certain features of Ada (such as type checking) to create a description that can be automatically verified for consistency Simulation is often an indispensable tool in the development of manufacturing systems. We show how a simulation of the operation of the manufacturing cell can be embedded in its description. Finally, we apply the methodology to a specific instance of a manufacturing cell.
Delayed write in a multilevel file system cache hierarchy offers a way to improve performance in diverse client/server scenarios, such as integrating mass store into a distributed file system or providing distributed file system access over low-speed links. Using file system traces and cache simulations, we explore extensions and modifications to the traditional client caching model employed in such file systems as AFS, Sprite, and DFS.High cache hit rates at an intermediate cache server-a machine logically interposed between clients and servers that provides cached file service to the clients-combined with high client cache hit rates lend practicality to an integrated mass storage file system. In such a system, magnetic tape or optical-based mass storage devices may be used as a first-class data repository, fronted by disk and RAM caches to offer acceptable access times to the large, but slow, mass storage system.Similarly, a high cache hit rate is necessary for users accessing file systems via low-speed links, where a delayed write intermediate caching server can mediate traffic to make better use of available bandwidth. In an example taken from mobile computing, an intermediate server might be used as a docking station at a user's home. This arrangement would be convenient for users of mobile computers who upload large amounts of data generated while operating in disconnected mode. Simulations of delayed write caching strategies are applicable to both the mass storage and low-speed link scenarios .A. Schill et al. (eds.), Distributed Platforms
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