SDI Seminar

Speaker: Yui-wah LEE, CUHK & CMU

Date: November 13, 1997

Where & When: WeH 8220, Noon

Operation-based Update Propagation in a Mobile File System


The update propagation of big files over low-bandwidth networks is a major bottleneck for mobile file systems. I, hereby, propose a new technique, {\em operation-based update propagation}, that would alleviate this bottleneck. The proposed technique is motivated by the following two observations: First, many big files are updated by typically small user operations. Second, many user operations can be re-executed cheaply. With these observations, I propose that a mobile client can propagate file updates by operations: It ships compact operations rather than the big files that these operations updated- The big files can be re-generated, after those operations have been shipped across the low-bandwidth network.

The idea is simple, but the real question is whether it is feasible in the context of file systems. In this talk, I will justify the feasibility of the proposed technique by giving preliminary answers to some key design questions. I will explain why logging of user operations does not necessarily imply rewriting all applications, and for some applications which do need rewriting, why we would expect only moderate amounts of rewriting. I will also explain how we could ensure that correctness would not be compromised by re-generations of files. Finally, I will outline my implementation plan of the proposed technique in the existing Coda file system.

(This talk is equivalent to my thesis-proposal talk for CUHK. You can find my thesis proposal at /afs/cs/user/clement/Public/

About the speaker: Mr. Yui-wah LEE (Clement) is a PhD student in the Department of Computer Science and Engineering, The Chinese University of Hong Kong (CUHK). He was invited by Professor M. Satyanarayanan to visit CMU last November, and he has been working with the Coda Group since then. He is returning to Hong Kong on Nov. 20 to continue of his study in CUHK.