Mobile File Systems P Sathiyamurthi P Sathiyamurthi Introduction

Mobile File Systems P. Sathiyamurthi

P. Sathiyamurthi Introduction n Overview of mobile file systems Characteristics that complicate file system operation for mobile applications Overview of Coda - How Coda deals with these complications

P. Sathiyamurthi Mobile File Systems n n n Allow mobile users to run applications that access shared files over a mobile network Applications behave the same regardless of where user is located Act as middleware between operating system and application

P. Sathiyamurthi Mobile vs. Stationary n n Resources for mobile devices never more than for stationary devices Mobility inherently hazardous Mobile device network connectivity highly variable in reliability and performance Mobile devices dependent on a finite energy source

P. Sathiyamurthi Autonomy vs. Interdependence n n Balance between autonomy and interdependence necessary for optimal system performance Adaptability = main goal of mobile file systems (compromise)

Mobile File Systems Characteristics n n n P. Sathiyamurthi Provide location transparency Provide replication (optimistic/pessimistic) Provide cache consistency Provide connected and disconnected operational modes Provide scalability

P. Sathiyamurthi MFS Modes of Operation

P. Sathiyamurthi Coda Distributed File System n n n Files grouped into volumes replicated on Coda servers Version stamping to resolve conflict Client caching reduces network dependence and provides scalability Uses optimistic approach Callbacks to maintain cache coherency

P. Sathiyamurthi Coda Client File Session

P. Sathiyamurthi Coda Client States

P. Sathiyamurthi Conclusions n n Data consistency, data caching, scalability, location transparency, data replication, and availability Adaptability to network

P. Sathiyamurthi References n Satyanarayanan, M. Fundamental Challenges in Mobile Computing. Fifteenth ACM Symposium on Princ. of Distr. Comp. May 1996. n Honeyman, P. , Huston, L. B. Communications and Consistency in Mobile File Systems. IEEE Personal Communications, Dec. 1995, pp. 44 -48. Braam, P. J. The Coda Distributed File System. Carnegie Mellon University. http: //www. coda. cs. cmu. edu/ljpaper/lj. html. Schiller, J. Mobile Communications (2 nd ed. ). Addison-Wesley, 2003, pp. 375 -381. Tanenbaum, A. S. , van Steen, M. Distributed Systems: Principles and Paradigms. Prentice Hall, 2002, pp. 604 -623. n n n

P. Sathiyamurthi