面向虚拟机的分布式块存储系统设计及实现

摘要

Traditional storages such as DAS, NAS, SAN and distributed file system are hard to meet all demands in the IaaS. Neither capacity, performance, availability nor price can be sacrificed, and a distributed block storage system is the only solution to this problem. By combining a local data volume, a remote data volume and a journal volume creatively, the system provides almost as much availability as the traditional 3-replica way, while reducing capacity usage. Performance is improved by writing journal and local data volume, and updating remote data volume in the background. Data transmission also reduces network overhead. The test result shows that the system provides all the IOPS and most of the bandwidth which the lower layer device supports, and failure tol-erance and recovery allows the I/O service going on with an acceptable performance without being interrupted.%传统的DAS、NAS、SAN存储以及分布式文件系统难以满足IaaS场景下的虚拟机存储对容量、性能、可用性的综合需求。设计一个分布式块存储系统，提供较高的性能和可用性、几乎不受限制的扩展性，同时保持低廉的价格，具有良好的前景。通过创新性地结合本地数据卷、远程数据卷和日志卷，系统达到了较传统的三副本技术（几乎）同等的可用性，同时减少了容量开销。并发写日志和本地数据卷、以及后台更新远程数据卷的方法提高了系统性能。将虚拟机所需的数据迁移到相应的宿主机上，可以提高虚拟机的性能表现。测试表明，系统提供了底层设备支持的全部IOPS和绝大部分的带宽，并在故障中具备容错和恢复能力，恢复过程中的性能表现完全可接受。