| There are more and more advanced processor architectures and CPU cores used in a computer system with the development of science and technology. In this case, virtual machine technology came into being to improve resource utilization. In practical application, virtual machine live migration has many advantages, such as, higher applicability, it can be used for online maintenance and upgrade for a server. It can also be used for the disaster recovery and load balancing. At the same time, it can be used to improve the performance and reliability of a server, and enhance the services scalability and manageability.In this thesis, the server mode was changed from the original stand-alone mode to the virtual machine mode according to our working circumstance. Thus it can decrease the quantity and improve the efficiency of physical machines used in practice. The power, space, and running cost were reduced to a great extent. The virtual machine live migration technology makes it possible to do the maintenance and upgrading works in working hours, but not in the night as usual. This can greatly reduce the operation errors.Among many popular virtual machine techniques, the Citrix XenServer was selected as a platform to study the live migration of a DNS server on a virtual machine. Three XenServer and one personal computer were used in this work. The personal computer was used as virtual machine remote control console with XenCenter installed in it. One XenServer was used as a resource pool, in which a virtual machine was created with Linux operating system to configure NFS service. This virtual machine acted as a shared storage SR, which was configured as the default shared storage in the range of pools. The other two XenServer joined the pool. One of them was the source server, in which a virtual machine was installed and a DNS service was configured and started. The running DNS server was migrated to another XenServer through the XenMotion module. And the migration performance was monitored.The migration performance on a 512M, 1024M memory DNS server was determined to test the effect of the memory capacity on the virtual machine migration. During the migration process, the value of memory keeps increasing, which indicates the main data is the memory during the migration. The VM will be run in the target server and the server state become green after the migration. In this experiment, the purpose was to test whether there was a service suspension or not during the migration and to obtain the total migration time. Keep pinging the server IP in the personal computer when migrate 512 M DNS. The response time is less than 1 ms before migration. Then the time suddenly increased to 45 ms as migration process going. And the time continues increasing until the average time reaches to 130 ms. Then the time reduced to 72 ms. At last the response time reduced to less than 1 ms after the migration done. No packet loss happened during the whole migration process. No interruption happened by querying DNS server with nslookup command. According to the experimental data, we can verify that the terminal user can not notice the interruption during dynamic migrating using XenServer. This realized a transparent migration. For a virtual machine, the memory capacity has no much effect on the offline time. However, the total migration time will increase with the memory capacity increasing.In conclusion, the advantage of the virtual machine technology is that the utilization of the existing server hardware resources was improved. In the practical application of the virtual machine technology, several issues must be solved. The first one is to transform the model of one service on one single physical machine into the model of multiple virtual machines sharing one single physical machine, i.e. P2V. Another problem is about management operations when using the virtual machine. That is how to make virtual machines work better and more secure. Because many services we provided can not be interrupted. Even those which can be interrupted, it needs to be maintained at night. In daily maintenance, it also involves data backup, load balancing and disaster recovery. All these works need to be implemented. Dynamic migration technology of XenServer can solve all the problems mentioned above. |
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