A Distributed Namespace for a Distributed File System

Abstract: Due to the rapid growth of data in recent years, distributed file systems have gained widespread adoption. The new breed of distributed file systems reliably store petabytes of data on commodity hardware, and also provide rich abstractions for massively parallel data analytics. The Hadoop Distributed File System (HDFS) is one such system which provides the storage layer for MapReduce, Hive, HBase and Mahout. The metadata server in HDFS, called the NameNode, is a centralized server which stores information about the whole namespace. The centralized architecture not only makes the NameNode a bottleneck and a single-point-of-failure, but also restricts the overall capacity of the filesystem. To solve the availability and scalability issues of HDFS, a new architecture is required. In this report, we propose a distributed implementation of the HDFS NameNode, where the filesystem metadata is stored in a distributed, in-memory, replicated database called MySQL Cluster. The NameNodes are state-less, and the throughput of the system can be increased by either adding NameNodes, or by adding more data nodes in NDB. HDFS clients can access the metadata by connecting to any one of the NameNodes. The evaluation section shows that the new architecture, as compared to HDFS, can handle more requests per second, store ten times more files and recover from failures within a few seconds.