Abstract
Sharing data in a mobile environment is realized through a number of techniques that can cope up with a range of network outages. The challenge includes making shared data highly available, and transparently accessible even as a user roams around in area of network coverage. Three different mechanisms that have been proposed in the past are: (i) relocatable dynamic object (RDO), (ii) replicated storage system and (iii) distributed file system with support for mobility and disconnection. In this chapter our focus is primarily on CODA. It provides a fully mobility transparent file system which is ideal from the application developers’ point of view. However, it requires considerable of support mechanisms to hide physical characteristics of wireless communication medium. CODA introduced queued remote procedure calls (QRPC), optimistic replica management and prefetching (hoarding) to provide a highly available mobility transparent file system based on well known distributed file system AFS. InterMezzo is a light weight filtering file system layer sitting between VFS and a native file system. So, in reality it is a stacked up file system layer over native file system. It mostly preserves protocols of CODA and AFS. So, this chapter mainly focuses on CODA.
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