中文摘要：

在云存储系统中使用客户端元数据缓存，不仅可以减轻元数据服务器的压力，避免元数据服务器成为系统瓶颈，提高系统的可扩展性，而且可以降低客户端元数据操作的响应延迟，极大地提高客户端IOPS性能。本文对云存储系统客户端元数据缓存同步机制进行研究，提出了基于更新日志的元数据缓存同步策略，利用该策略替代了Mass Cloud云存储系统原先的元数据缓存完全同步策略。测试结果表明．新的缓存同步策略给Mass Cloud云存储系统带来了20-140倍的性能提升。

英文摘要：

Client-side metadata cache is used in cloud storage system. It can not only reduce the work load of metadata server, solve the bottleneck prohlem of metadata server, and improve the expandability of cloud-storage system, hut also reduce the response latency of client-side metadata request, improve client-side IOPS-performanee greatly. This paper does research on synchronization mechanism of metadata caches in cloud storage system, puts forward the synchronization strategy based on change-log. This strategy is used to replace the original full-synchronization strategy in the cloud storage system named MassCloud. The results of test show that this stragety brings about 20-140 times performance improvement to MassCloud storage system.