Orchestra: Extensible Block-level Support for Resource and Data Sharing in Networked Storage Systems

High-performance storage systems are evolving towards decentralized commodity clusters that can scale in capacity, processing power, and network throughput. Building such systems requires: (a) Sharing physical resources among ap-plications; (b) Sharing data among applications; (c) Allow-ing customized views of data for applications. Current solutions satisfy typically the first two require-ments through a distributed file-system, resulting in mono-lithic, hard-to-manage storage systems. In this paper, we present Orchestra, a novel storage system that addresses all three above requirements below the file-system by extending the block layer. To provide customized views, Orchestra al-lows applications to create semantically-rich virtual block devices by combining simpler ones. To achieve efficient re-source and data sharing it supports block-level allocation and byte-range locking as in-band mechanisms. We implement Orchestra under Linux and use it to build a shared cluster file-system. We evaluate it on a 16-node cluster, finding that the flexibility offered by Orchestra in-troduces little overhead beyond mandatory communication and disk access costs.