Scalability of Replicated Metadata Services in Distributed File Systems

International audienceThere has been considerable interest recently in the use of highly-available configuration management services based on the Paxos family of algorithms to address long-standing problems in the management of large-scale heterogeneous distributed systems. These problems include providing distributed locking services, determining group membership, electing a leader, managing configuration parameters, etc. While these services are finding their way into the management of distributed middleware systems and data centers in general, there are still areas of applicability that remain largely unexplored. One such area is the management of metadata in distributed file systems. In this paper we show that a Paxos-based approach to building metadata services in distributed file systems can achieve high availability without incurring a performance penalty. Moreover, we demonstrate that it is easy to retrofit such an approach to existing systems (such as PVFS and HDFS) that currently use different approaches to availability. Our overall approach is based on the use of a general-purpose Paxos-compatible component (the embedded Oracle Berkeley database) along with a methodology for making it interoperate with existing distributed file system metadata services