Tools and Techniques for Managing Virtual Machine Images

Virtual machines can have many different deployment scenarios and therefore may require generation of multiple VM images. OS Farm is a service that aims to provide VM images that are tailored and generated on the fly. In order to optimize generation of images, a layered copy-on-write image structure is used, and an image cache ensures that identical images are not regenerated. Images can be several hundreds of megabytes large and thus can congest the network and delay their transfer. Content-Based Transfer is a technique which transfers only the difference between the source image and existing target client image data. We present an implementation which achieves an observed bandwidth close to the theoretical maximum and a significant reduction in network congestion.