Exploiting Weak Connectivity for Mobile File Access
Lily B. Mummert, Maria R. Ebling, M. Satyanarayanan
Weak connectivity, in the form of intermittent, low-bandwidth, or
expensive networks is a fact of life in mobile computing. In this paper,
we describe how the Coda File System has been evolved to exploit such networks.
The underlying theme of this evolution has been the identification of hidden
assumptions about strong connectivity, and their systematic elimination
through the introduction of adaptivity. Many aspects of the system,
including communication, cache validation, update propagation and cache
miss handling have been affected. As a result, Coda is able to provide
good performance to users even when network bandwidth varies over four
orders of magnitude --- from modem speeds to LAN speeds. Users are affected
by network quality mainly in the promptness with which updates are propagated,
and in the degree of transparency with which cache misses are handled.