Research And Implementation Based On Techonology Of Xen Virtual Block Device

Virtualization serves as supporting technology for cloud computing.It plays very important role in data center.Cloud service provider can improve the rate of utilization of physical devices in both public cloud and private cloud.What's more,using virtualization's migration technology,administrators can do system redundance and backup.Block device is an irreplaceable device for virtual operating system.It has linear addressing ability.Disk is the most popular block device.It serves in datacenter in forms of local storage or network attached storage.However block device becomes bottleneck that restricts efficiency of virtualization in both of the forms.One of the big shortage is that administrator always try to decrease redundancy of physical data centers to improve utilization of physical resource.But requirement for features of operating system's application arrangement,full system migration,storage's backup is coming more and more strongly.Block device's I/O ability is always weak compared with CPU or memory,and always the network redundancy is comparatively low,which challenge a lot for fulfilling the requirements talked above with high efficiency.As an important open source project of virtualization,Xen attacts lots of attention with its high efficiency.However analysis for source code of Xen is very few in theoretical area.This paper does a lot of theoretical survey and analyzes lots of source code for Xen.Then this paper goes a further step and analyzes Xen source code of block device's virtualization thoroughly and makes a good summary for Xen's virtual block device's working mechanism.Technology of virtual machine's migration is widely used in data centers,based on which,administrators can migrate VMs or do redundancy backup.Based on analysis for Xen virtual block device,the focus of this paper is to analyze Xen's mechanism of processing storage's I/O requests and then raising approach called "Partners Assisted Storage Migration"(PASM)to improve the efficiency of virtual machines' storage migration,using PASM,administrators can release the drastic challenge between storage migration and virtual machines' storage I/O operation.This paper also gives solution of "cold mounting" to improve the efficiency of arranging applications on virtual blocks;besides that this paper incorporates Rsync,an open source project,to Xen to fulfill system block device's incremental backup,thus releases the network a lot.This paper raises some still existing problems for block device of virtualization,and gives some directions for future work.