动态盘阵D/H分布与基于控制理论的在线重构

D/H Placement and On-Line Data Reorganization Based on Control Theory in Dynamic Disk Array

由于能够提供高性能I/O,盘阵被广泛采用.但以往的盘阵扩展性不足.而用户或应用程序对外存容量和I/O性能需求是变化的,盘阵系统本身必须有很强的扩展性,以适应系统的I/O需求.因此,由于既具有盘阵的高性能I/O,又能通过增加或减去设备后进行数据重构实现性能的扩展,动态盘阵具有广泛的前景.动态盘阵的技术热点是数据分布算法和在线自适应数据重构技术,使得盘阵的性能和容量能够随着系统的扩展而伸缩,同时使得盘阵动态扩展时的数据重构对系统的影响非常小.主要工作是:第1,对动态盘阵的数据分布展开研究,并提出一种新的数据分布算法(D/H分布).在D/H分布中,盘阵扩展时始终保持各设备上空间和负载的平衡性,同时扩展时重构的数据最少;第2,针对D/H分布,提出基于控制理论的数据重构技术,使得盘阵动态扩展时的在线数据重构对请求QoS的影响非常小,同时使得数据重构能够尽快完成;第3,研究中针对Sprite trace和合成负载进行了大量模拟实验,结果表明,提出的基于控制理论的数据重构技术行之有效.

Disk Array is adopted widely because of its high performance I/O. To adapt the need of applications' changeable I/O performance, I/O storage subsystem should be highly scalable. So DDA (dynamic disk array), which can scale adaptively, is an ideal system. The key technology of DDA is its data placement algorithm and online data reorganization algorithm. The main contribution of the paper is: first, a detailed study on DDA data placement is conducted and a new placement method, D/H, is presented. In D/H placement, the space in DDA is balanced after scale, and the reorganization cost is minimized; then, an online data reorganization algorithm based on control feedback theory is provided. With this strategy, the reorganization in DDA does little impression to the system QoS, and under this condition, data reorganization can be accomplished as quickly as possible; finally, simulation results show that Online Data Reorganization based on Control Theory is useful.