Large Granularity Cache Coherence for Intermittent
Connectivity
L. Mummert, M. Satyanarayanan
Abstract
To function in mobile computing environments, distributed file systems
must cope with networks that are slow, intermittent, or both. Intermittence
vitiates the effectiveness of callback-based cache coherence schemes in
reducing client-server communication, because clients must validate files
when connections are reestablished. In this paper we show how maintaining
cache coherence at a large granularity alleviates this problem.
We report on the implementation and performance of large granularity cache
coherence for the Coda File System. Our measurements confirm the value
of this technique. At 9.6 Kbps, this technique takes only 4 -- 20% of the
time required by two other strategies to validate the cache for a sample
of Coda users. Even at this speed, the network is effectively eliminated
as the bottleneck for cache validation.