Research On Live Migration Of Virtual Machine Across The Datacenter

Virtualization is used to manage resources in the Datacenter. Virtual Machine livemigration can move the application between the hardware; make managementmechanism have ability to sharing resource, scheduling resource, disaster tolerance,dynamic integration, and improving service quality, security, and utilization of thewhole data center. Virtual Machine live migration can only be limited in the Local AreaNetwork, different Virtual Machine share image files which are stored in distributed filesystem via LAN, due to the large bandwidth and low latency in LAN, can guarantee thequality of service to users.Across the Datacenter, not only need to manage resource within one data center,but also need to unify manages multiple datacenters which widely distributed ongeographical location. Because of low bandwidth and high delay of network betweendatacenters, when image files are shared by datacenters, I/O access virtual machineimages remotely should be conducted in virtual machine, which reduced efficiency.Therefore, Virtual Private Network of connecting multiple datacenters is needed to bedesigned, to break boundaries between multiple datacenters and guarantee the safety ofdatacenter after interconnected using its perfect security technology. Live migration ofvirtual machine with image file is designed based on XEN virtual machine migrationmechanism. Image file’s strong expansion capability of Qcow mechanism and templateimage’s sharing mechanism make that virtual machine doesn’t have to send templateimages during migration and needn’t send the number of image file at GB level. Entirecontents of the Qcow file are sent to file system of destination before the start ofmemory iteration. The write operation of virtual machine to Qcow file is monitored inreal time in the process of memory iterative and dirty blocks are also recorded.Memory dirty pages and dirty block are together sent to destination node at the end ofeach iteration and destination node will map data to corresponding position by callingmemory mapping and disk drive after data is received. Dirty pages produced by virtualmachine with heavy load are reduced through optimizing the process of memoryiterative. Hash value of file content of each monitoring record is also recorded and saved in cache and files including same Hash value should be sent only once whichreduced the amount of data transferred.Virtual machine live migration mechanism across datacenter proposed in this papercould realize virtual machine live migration on the premise of normal operation of thebusiness, which provides a basis method for the resource management of datacenter.Total migration time is less than120seconds and downtime is less than5seconds at thebest case. But the size of Qcow file is the key factor that decided total time of migration,along with the expand of file，migration time is proportional increase.