Analyzing Metadata Performance in Distributed File Systems

Abstract

Distributed file systems are important building blocks in modern computing environments.The challenge of increasing I/O bandwidth to files has been largely resolved by the use of parallel file systems and sufficient hardware. However, determining the best means by which to manage large amounts of metadata, which contains information about files and directories stored in a distributed file system, has proved a more difficult challenge.The objective of this thesis is to analyze the role of metadata and present past and current implementations and access semantics. Understanding the development of the current file system interfaces and functionality is a key to understanding their performance limitations.Based on this analysis, a distributed metadata benchmark termed DMetabench is presented.DMetabench significantly improves on existing benchmarks and allows stress on metadata operations in a distributed file system in a parallelized manner. Both intra-node and inter-node parallelity, current trends in computer architecture, can be explicitly tested with DMetabench. This is due to the fact that a distributed file system can have different semantics inside a client node rather than semantics between multiple nodes.As measurements in larger distributed environments may exhibit performance artifacts difficult to explain by reference to average numbers, DMetabench uses a time-logging technique to record time-related changes in the performance of metadata operations and also protocols additional details of the runtime environment for post-benchmark analysis.Using the large production file systems at the Leibniz Supercomputing Center (LRZ) in Munich, the functionality of DMetabench is evaluated by means of measurements on different distributed file systems. The results not only demonstrate the effectiveness of the methods proposed but also provide unique insight into the current state of metadata performance in modern file systems.The thesis concludes with a discussion of the results and the identification of areas for future research. ii

Towards a fast and secure design for enterprise‐oriented cloud storage systems

“…This information is called the metadata. 11 Although the size of metadata is generally small compared to the overall storage capacity of the distributed file system, 50% to 80% of all file system accesses are to metadata. 12 So efficient metadata management is a critical aspect of overall system performance in the distributed file system.…”

“…To distinguish the right file server that a specific file is located on, the distributed file system is required to provide some information about the relationship between the file and its storage location. This information is called the metadata . Although the size of metadata is generally small compared to the overall storage capacity of the distributed file system, 50 % to 80 % of all file system accesses are to metadata .…”

DMFSsim: A Distributed Metadata File System Simulator

“…Optimizing these metadata-intensive operations becomes increasingly important. There is some work on the optimization of metadata-intensive operation, aiming at improving the efficiency of these metadata operations [9,10]. However, the number of servers used in their experiments is low, typically at most two or three dozens, insufficient to illustrate related problems with hundreds or thousands of servers typical in real HEC centres.…”