Eager Computation and Lazy Propagation of Modifications for Reducing Synchronization Overhead in File Replication System

Files are typically replicated in a distributed system to improve the data access, response time, data availability and increase fault tolerance capability. Many researchers discusses about the applications that works on read only data, however many applications need to alter the data. If all replicas of a file are not synchronized this drives the system into inconsistent state. To keep system consistent, the changes made at one replica of a file should be reflected in other replicas in minimum time, this time is called synchronization overhead. Proposed approach reduces this overhead by using lazy update propagation and ordered storage of updates. Unlike conventional approaches that propagate the updates to a fixed master replica of a file, the proposed approach transfer the role of master replica to the last modified replica. This mechanism reduces the overhead of propagating the update messages to master replica immediately. The master replica computes the modification messages eagerly but propagates lazily. Experimental results shows how various factors viz., file size, size of modifications and number of replicas to be updated affects the time to propagate the changes to other replicas.