Users of hosted web-based applications implicitly trust that those applications, and the data that is within them, will remain active and available indefinitely into the future. When a service is terminated, for reasons such as the insolvency of the business that is providing it, users risk the immediate loss of software functionality and may face the permanent loss of their own data. This paper presents Micasa, a runtime for hosted applications that allows a significant subset of application logic and user data to remain available even in the event of the failure of a provider's business. By allowing users to audit application dependence on hosted components, and maintain externalized and private copies of their own data and the logic that allows access to it, we believe that Micasa is a first step in the direction of a more balanced degree of trust and investment between application providers and their users.

As hardware parallelism continues to increase, CPU caches can no longer be considered as a transparent, hardware-level performance optimization. Cache impact on performance, in particular in the face of false sharing, is completely dependent on the software that is executing. To effectively support parallel workloads on cache coherent hardware, the operating system must begin to treat the CPU cache like other shared hardware resources, and manage it appropriately.

We collected file system content data from 857 desktop computers at Microsoft over a span of 4 weeks. We analyzed the data to determine the relative efficacy of data deduplication, particularly considering whole-file versus block-level elimination of redundancy. We found that whole-file deduplication achieves about three quarters of the space savings of the most aggressive block-level deduplication for storage of live file systems, and 87% of the savings for backup images. We also studied file fragmentation, finding that it is not prevalent, and updated prior file system metadata studies, finding that the distribution of file sizes continues to skew toward very large unstructured files.

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.