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 applications; (b)Sharing data among applications; (c) Allowing customized views of data for applications. Current solutions satisfy typically the first two requirements through a distributed file-system, resulting in monolithic, 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 allows applications to create semantically-rich virtual block devices by combining simpler ones. To achieve efficient resource 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 introduces little overhead beyond mandatory communication and disk access costs.