| Today's computer environments, which include operating systems, applications, settings, and documents, are tied to a computer and often custom created for that computer. The result is difficulties for the user: each computer must be individually managed at the expense of time and money, users have limited ability to move between computers, and recovering from a hardware failure can be time consuming or even impossible.; This work proposes and evaluates an architecture called the Collective that addresses these difficulties. With the help of virtual machine monitors, the Collective creates and manages entire computer environments as a data type called a capsule. The Collective stores multiple versions of these capsules in network storage, where they can be pulled down and run by any authorized computer.; To simplify management, the Collective introduces a special kind of capsule called a virtual appliance. The software in a virtual appliance is defined by a publisher on behalf of its subscribers. In most appliances, subscribers cannot install software. As a result, the Collective can ensure that the software in the virtual appliance closely follows what is published by the publisher, increasing the predictability of the appliance's behavior. Two features that result from this design are automatic updates and rejuvenation. On reboot, the Collective discards changes and reverts back to the latest published version of the appliance. Virtual appliances keep per-subscriber data in storage that is not reverted.; Capsules are large, potentially gigabytes in size. This dissertation describes and evaluates optimizations for transferring capsules efficiently. Experience using a prototype of the Collective suggests that the Collective is a practical way of carrying computing environments between computers and managing the software and configuration of far-flung computing environments. |
