AN ENHANCEMENT LAZY REPLICATION TECHNIQUE FOR HADOOP DISTRIBUTED FILE SYSTEM

The Hadoop Distributed File System (HDFS) is designed to store, analysis, transfer larg datasets reliably, and stream it at high bandwidth to the user applications. HDFS is a variant of the Google File System (GFS). It handles fault tolerance by using data replication, where each data block is replicated and stored on multiple DataNodes. Therefore, the HDFS supports availability and reliability. The existed implementation of the HDFS in Hadoop performs replication in a pipelined manner that takes much time for replication. In this paper, an alternative technique for efficient replica placement, called Enhancement Lazy replication technique, has been proposed. The main principle of this technique is that, the client allows to write a block to two DataNodes in parallel, which store the packet. which will send acknowledgement directly to the client without waiting of receiving acknowledgement from other DataNodes. The experiment has been performed to evaluate the performance of the proposed HDFS replication technique with the default pipelined replication technique and the existed replication techniques; using TestDFSIO benchmark. According to the experimental results (i.e., the execution time and throughput), it is found that the HDFS availability has been improved in the proposed replication technique.