Experience with Disconnected Operation in a Mobile Computing Environment

Experience with Disconnected Operation in a Mobile Computing Environment

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Unformatted text preview: Experience with Disconnected Operation in a Mobile Computing Environment M. Satyanarayanan, James J. Kistler, Lily B. Mummert, Maria R. Ebling, Puneet Kumar, Qi Lu June 1993 CMU-CS-93-168 School of Computer Science Carnegie Mellon University Pittsburgh, PA 15213 To appear in Proceedings of the 1993 USENIX Symposium on Mobile and Location-Independent Computing, Cambridge, MA, August 1993 Abstract In this paper we present qualitative and quantitative data on file access in a mobile computing environment. This information is based on actual usage experience with the Coda File System over a period of about two years. Our experience confirms the viability and effectiveness of disconnected operation. It also exposes certain deficiencies of the current implementation of Coda, and identifies new functionality that would enhance its usefulness for mobile computing. The paper concludes with a description of what we are doing to address these issues. This work was supported by the Advanced Research Projects Agency (Avionics Laboratory, Wright Research and Development Center, Aeronautical Systems Division(AFSC), U.S. Air Force, Wright-Patterson AFB under Contract F33615-90-C-1465, Arpa Order No. 7597), the National Science Foundation (Grant ECD 8907068), IBM, Digital Equipment Corporation, and Bellcore. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either express or implied, of the U.S. Government, IBM Corporation, Digital Equipment Corporation, or Bellcore. Keywords: Disconnected operation, Coda File System, mobile computing, wireless communication, performance evaluation, hoarding, reintegration, file reference traces, weak connectivity, conflict resolution, transactions 1. Introduction Portable computers are commonplace today. In conjunction with high- and low-bandwidth cordless networking technology, such computers will soon provide a pervasive hardware base for mobile computing . A key requirement of this new world of computing will be the ability to access critical data regardless of location. Data from shared file systems must be made available to programs running on mobile computers. But mobility poses serious impediments to meeting this requirement. We begin this paper by describing how shared file access is complicated by the constraints of mobile computing. We then show how the design of the Coda File System addresses these constraints. The bulk of the paper focuses on our usage experience with Coda. We present qualitative and quantitative data that shed light on Codas design choices. Based on our experience, we have identified a number of ways in which Coda could be improved. The paper concludes with a description of our current work along these dimensions....
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This note was uploaded on 10/19/2009 for the course CNT 5517 taught by Professor Helal during the Fall '09 term at University of Florida.

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Experience with Disconnected Operation in a Mobile Computing Environment

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