Aiming to distributed computing and data centralizing storage in large-scale network computing environments and combining sparse and bursting characteristic of COW(copy-on-write) disk storing modified data blocks,the distributed COW network disk architecture was presented. The system building process of network computing environments was speeded up by apportioning the aggregation spending that server manages all related COW disks of client hosts to each client host A improving 64bit bitmap compress arithmetic was designed to reduce the size of COW disk's bitmap,so server disk space was saved and the network communication spending of distributed COW disk was less. The modified prefetching arithmetic based on COW bursting blocks was presented to improve the hit rate of Cache relating with distributed COW disk. Experiments on the prototype show that the distributed COW mechanism can effectively reduce system building latency of multi-client hosts network computing environment based on improving COW bitmap compress and prefetching arithmetic.%针对大规模网络计算环境的分布式计算和数据集中存储特点,结合COW(copy-on-write)磁盘记录改写块的稀疏和突发特性,提出了一种分布式COW网络盘体系结构,将服务器处理所有客户主机相应COW盘的聚合开销分摊到各个客户主机自身,以加速网络计算环境系统构建速度；设计了一种改进的64bit位图压缩算法以有效减少COW盘位图文件大小,节省服务器磁盘空间和降低分布式COW盘网络传输开销；提出一种适合COW盘改写块突发特性的预取算法,以提高分布式COW盘相应Cache的命中率.实验结果表明基于改进的COW位图压缩和预取算法实现的分布式COW盘降低了多客户主机网络计算环境构建延迟.
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