OS virtualization is drastically changing the face of system administration for large computer installations such as commercial datacenters and scientific clusters. A recent report by Gartner predicts that commercial use of

Abstract. This paper describes Olive, the first distributed block storage system to provide consistent pointin-time branching. Point-in-time branching allows users to recursively and quickly snapshot or clone the storage state. It has a wide range of applications including testing new deployments or upgrades without disrupting a running system, quickly provisioning large homogeneous systems, and preserving old versions of data. Olive provides block-level access and strong consistency for broad applicability, allowing it to branch file systems, database systems, and every other storage application that ultimately stores data on block storage. Olive is distributed and replicated to provide fault tolerance and availability. Providing strong consistency for branching in a replicated distributed system is a technical challenge that we address in this work. We evaluate Olive and show that branching typically takes a few tens of milliseconds, and so it has little impact on I/O’s. 1

Parallax is a distributed storage system that uses virtualization to provide storage facilities specifically for virtual environments. The system employs a novel architecture in which storage features that have traditionally been implemented directly on high-end storage arrays and switches are relocated into a federation of storage VMs, sharing the same physical hosts as the VMs that they serve. This architecture retains the single administrative domain and OS agnosticism achieved by array- and switch-based approaches, while lowering the bar on hardware requirements and facilitating the development of new features. Parallax offers a comprehensive set of storage features including frequent, low-overhead snapshot of virtual disks, the “gold-mastering ” of template images, and the ability to use local disks as a persistent cache to dampen burst demand on networked storage.

A complex challenge in mobile computing is to allow the user to migrate her highly customised environment while moving to a different location and to continue work without interruption. I motivate why this is a highly desirable capability and conduct a survey of the current approaches towards this goal and explain their limitations. I then propose a new architecture to support user mobility by live migration of a user’s operating system instance over the network. Previous work includes the Collective and Internet Suspend/Resume projects that have addressed migration of a user’s environment by suspending the running state and resuming it at a later time. In contrast to previous work, this work addresses live migration of a user’s operating system instance across wide area links. Live migration is done by performing most of the migration while the operating system is still running, achieving very little downtime and preserving all network connectivity. I developed an initial proof of concept of this solution. It relies on migrating whole operating systems using the Xen virtual machine and provides a way to perform live migration of persistent storage as well as the network connections across subnets. These

volume management for virtual machines by