Research On Availability Of Virtual Machine Hot Standby Based On Double Shadow Page Tables

In recent years, virtualization technology has been widely used in the data center, system security, load balancing and server management integration for its independence, high resource utilization and ease of management concern. In virtualized environment, physical function virtual some virtual machines through the virtual machine monitor to provide services for users. With the development of virtualization technology, the reliability of virtual machine has been an important factor to hinder the development of virtual machine technology. By means of the independence the cross-platform portability of virtual machine, and the characteristic of independent with underlying hardware in hot standby technology. The program of master-slave replication (Primary-Backup) has become one of the important means to protect the virtual machine in high reliability, which is by building a backup virtual machine to reduce the probability of system failure and increase the reliability of the virtual machine, to achieve a low-cost and efficient fault tolerance mechanisms of virtual machine.Meanwhile, the suspension of virtual machine and the "destruction-reconstruction" of the shadow page table during the process of the traditional hot standby lead to the virtual machine availability discounted, therefore, how to improve the availability of virtual machine during its hot standby has become a pressing problem. virtual machine technology Xen, VMware, KVM have make a research about it.This paper describes the background, status, significance and the key technology of virtual machine, and then, example some typical virtual machine, focuses on the traditional hot standby technology Remus which is based on Xen. Zero Downtime based on Double Shadow Page Tables method based on Most Recently Used algorithm is presented to solve low availability caused by the copy technology in the output delay in the virtual machine hot standby. This method use check-pointing mechanism, and the workflow of the primary Virtual Machine is divided into two stages:running and synchronization. One of the two Shadow Page Tables is as the main table, the other is as the alternate table. During the running stage of the primary Virtual Machine,the main table is used to save the operation of the virtual machine, in order to reduce the time of Shadow Page Table’s building after Synchronization, the primary Virtual Machine use the Most Recently Used algorithm to check out the suitable pages and save them in the alternate table. During the synchronization stage, the previous main table is used to realize the synchronization of the two Virtual Machines, and the previous alternate table is the main table, which can avoid the pause during the synchronization of the two Virtual Machines. Experimental results show that Zero Downtime and Double Shadow Page Table compared with the original method Remus in Xen4.0has obvious advantages.