云计算虚拟化环境下开源镜像对比分析

摘要

In cloud computing environment, open source VM images in formats of raw and qcow2 have been the mainstream of current application.Through experimental study, in this paper we make a detailed analysis on the functionality, network transmission and I/O performance of VM image formats.Experimental results show that qcow2 is conspicuously better than raw in terms of functionality and network transmission.In perspective of performance, the I/O performance of qcow2 is worse than that of raw owing to relatively simple addressing mode of raw.Experiments also show that when the I/O of file size exceeds half the memory of the VM, huge performance degradation appears on both VM image formats.Due to the influence of different caching mechanism, there is more serious impact on qcow2.%在云计算环境中，raw格式与qcow2格式等开源镜像已成为当前应用中的主流。通过实验研究，在功能、网络传输、性能等方面进行详细分析，实验结果表明qcow2的功能特性以及传输特性显著优于raw格式，在性能方面，raw格式因其寻址方式相对简单，读写性能相比qcow2格式较好。实验同时显示在超过虚拟机内存一半的文件读写情况下，两种格式均存在巨大性能衰减。因缓存机制不同的影响，此时raw格式的性能衰减好于qcow2。