SDI Seminar

Speaker: Yui-wah Lee (Clement), The Chinese University of Hong Kong

Date: June 3, 1999
Time: Noon
Place: Wean Hall 8220

Operation-based Update Propagation in a Mobile File System


This talk comprises two parts. The first part is a drill talk for our paper to be presented in the 1999 USENIX Annual Technical Conference, and I will describe a technique called {\em operation-based update propagation} (or operation shipping for brevity) for efficiently transmitting updates to large files that have been modified on a weakly connected client of a distributed file system. In this technique, modifications are captured above the file-system layer at the client, shipped to a surrogate client that is strongly connected to a server, re-executed at the surrogate, and the resulting files transmitted from the surrogate to the server. If re-execution fails to produce a file identical to the original, the system falls back to shipping the file from the client over the slow network. We have implemented a prototype of this mechanism in the Coda File System on Linux, and demonstrated performance improvements ranging from 40 percents to nearly three orders of magnitude in reduced network traffic and elapsed time. We also found a novel use of forward error correction in this context. (Joint work with K.S. Leung (CUHK) and M. Satyanarayanan (CMU)).

In the second part, I will briefly describe my on-going work on application-aware operation shipping. I will discuss how I enable a particular application -- the GIMP (the GNU Image Manipulation Program) -- to log user operations, and how Coda can co-operate with the GIMP to ship them. I will also give a demonstration on a preliminary prototype of an operation-logging GIMP.


Yui-wah Lee (Clement) is a PhD student in the Chinese University of Hong Kong. He was also a visiting student in the Coda group during the period from Nov. 1996 to Nov. 1997.