An Efficient I/O-Redirection-Based Reconstruction Scheme for Erasure-Coded Storage Clusters
An Efficient I/O-Redirection-Based Reconstruction Scheme for Erasure-Coded Storage Clusters
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DOI：
10.1109/tc.2015.2394399
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发表时间：
2015-11
影响因子：
3.7
通讯作者：
Jianzhong Huang;X. Qin;Xianhai Liang;C. Xie
中科院分区：
文献类型：
--
作者：
Jianzhong Huang;X. Qin;Xianhai Liang;C. Xie
本文讨论了在擦除编码存储集群的在线重建中遇到的I/O干扰问题，其中用户I/O与重建I/O竞争磁盘和网络带宽。我们提出了一种名为“RAM-RS”的重定向方案，以最大限度地减少用户和重建请求之间的I/O干扰。RAM-RS将针对故障节点的用户读/写重定向到RS编码的RAM区域，该区域由以RS编码方式在幸存节点中预分配的主存储器形成。RS编码的RAM区域可快速处理所有用户读/写未命中;因此，重建节点可以将其磁盘和网络带宽用于节点重建。RAM区域大大减少了由重建节点重建的数据量，因为（1）在RAM区域中缓冲未命中的写入，以及（2）通过使用幸存的节点来共同重建故障块来满足未命中的读取。我们建立了两个马尔可夫模型来估计RAM-RS系统的可靠性。建模结果表明，在一个存储集群中的RS编码的RAM区域的MTTDL大于由幸存的节点组成的相同的集群。我们实现了RAM-RS和传统的重定向方案在一个擦除编码的存储集群，现实世界的I/O跟踪重放。实验结果表明，与运行在9节点存储集群上的重定向方案相比，RAM-RS在用户响应时间和重建时间方面分别提高了1.78和1.20倍的系统性能。
This paper addresses an I/O interference problem encountered in on-line reconstruction of erasure-coded storage clusters, where user I/Os compete with reconstruction I/Os for both disk and network bandwidth. We propose a redirection scheme called `RAM-RS' to minimize the I/O interference among user and reconstruction requests. RAM-RS redirects user read/writes targeted at failed nodes to an RS-coded RAM region, which is formed by pre-allocated main memory in surviving nodes in the RS-coding manner. The RS-coded RAM region quickly serves all user read/write misses; therefore, a rebuilding node can devote its disk and network bandwidths to the node reconstruction. The RAM region substantially reduces the amount of data rebuilt by the rebuilding node, because (1) missed writes are buffered in the RAM region and (2) missed reads are satisfied by using surviving nodes to co-rebuild failed blocks. We build two Markov models to estimate the reliability of the RAM-RS system. Modeling results demonstrate that the MTTDL of RS-coded RAM region in a storage cluster is larger than that of the same cluster comprised of surviving nodes. We implement both RAM-RS and the traditional Redirection schemes in an erasure-coded storage cluster, on which real-world I/O traces are replayed. Experimental results show that compared with the Redirection scheme running on a 9-node storage cluster, RAM-RS improves system performance in terms of both user response time and reconstruction time by a factor of 1.78 and 1.20, respectively.