Filesystems for Network-Attached Secure Disks (CMU-CS-97-118)

Network-attached storage enables network-striped data transfers directly between client and storage to pro vide clients with scalable bandwidth on large transfers. Network-attached storage also decouples policy and enforcement of access control, avoiding unnecessary reverification of protection checks, reducing file manager work and increasing scalability. It eliminates the expense of a server computer devoted to copying data between peripheral network and client network. This architecture better matches storage technology's sus tained data rates, now 80 Mb/s and growing at 40% per year. Finally, it enables self-managing storage to counter the increasing cost of data management. The availability of cost-effective network-attached storage depends on it becoming a storage commodity, which in turn depends on its utility to a broad segment of the storage market. Specifically, multiple distributed and parallel filesystems must benefit from network-attached storage's requirement for secure, direct access between client and storage, for reusable, asynchronous access protection checks, and for increased license to efficiently manage underlying storage media. In this paper, we describe a prototype network-attached secure disk interface and filesystems adapted to network-attached stor age implementing Sun's NFS, Transarc's AFS, a network-striped NFS variant, and an informed prefetching NFS variant. Our experimental implementations demonstrate bandwidth and workload scaling and aggressive optimization of application access patterns. Our experience with applications and filesystems adapted to run on network-attached secure disks emphasizes the much greater cost of client network messaging relative to peripheral bus messaging, which offsets some of the expected scaling results.