| Virtualization is a broad definition, which means translating physical resource into resource which can be managed in logic. In virtualization, all resources can run on various kinds of physical platforms transparently, and the management of resource will be in progress according to their corresponding logical ways, to completely realize the automatic configuration of the resource. Virtualization can not only help user merge lots of working load by running various kinds of operation systems in one single operation system, but also improve the usability of the system and migrate virtual environment among systems.In order to reduce migration time and downtime of live migration, Xen use Pre-Copy algorithm to choose the appropriate time to stop virtual machine running and copy memory pages. Its core idea is that Xen will hang up process and transmit core data after part or the whole of the address space is transmitted completely from the source host to the target host. This algorithm in the empty load and low load performs perfectly, but not very well in high load,and the main reason is in high load, Pre-Copy algorithm is trapped in replicate iteration, until up to the maximum number of copies iteration.This paper uses Xen as the experiment platform to research the improvement and optimization of virtual machine's live migration, and it emphasis on to advance copies of the algorithm of shortcomings and the insufficiency, put forward a new algorithm to optimize the migration time and downtime. The work of this paper is listed as follows:1)Research and analysis on the virtual machine technology from the historical background, applications and technology in three aspects,and summarize some popular virtual machines nowadays.2)Research the principle and implementation of live migration based on Xen. This paper firstly introduces the concept and several technical problems of live migration, and then introduces its main contents and detailed process, finally analyses the whole process of live migration combining with Xen's source code.3)According to Xen's migration framework, put forward the page-layering algorithm based on the Pre-Copy algorithm. Key point of page-layering algorithm is to solve the problem of repeatedly copying the same dirty page in traditional iteration process,by counting the rewriting number of memory pages to reduce unnecessary copy.4)Verify the rationality and feasibility of page-layering algorithm designed by this paper through the experiments. In order to verify the robustness and stability of page- layering algorithm, this paper did experiment in low load, high memory load, high CPU load and high network load, and the experiments result shows that, the page-copying algorithm is can effectively optimize the total migration time and downtime in high dirty pages rate situation.5)Finally prospect the future trend and further application of virtual machine's live migration. |
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