Redundancy Aware Virtual Disk Mobility for Cloud Computing

With multiplicity of Cloud service providers offering geographically distributed Compute Clouds, both providers and customers find it necessary to quickly move virtual machine images between data centers. This is usually accomplished using standard rsync-based transfer which is slow and bandwidth intensive given large size of virtual machine images. This article proposes a mechanism to reconstitute an image on target data center using information about overlap among images and content already available in the target data center. No changes to file system are needed and the approach can immediately be used with traditional libraries storing images as regular files. Moreover, we use a peer-to-peer approach that allows simultaneous retrieval of fragments from multiple data centers. The system and algorithms have been implemented and evaluated on two Compute Cloud environments using three image libraries representative for a typical service provider. The evaluation shows an average 6 times reduction in terms of network transfer volume and time and can result in even larger reductions in case of images with small configuration changes.