Operation-based Update Propagation in a Mobile File
System
Yui-Wah Le, Kwong-Sak Leung, Mahadev Satyanarayanan
Abstract
In this paper we describe a technique called operationbased update propagation
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.