Abstractions as the Foundation for Storage Infrastructure John MacCormick, Nick Murphy, Marc Najork, Chandramohan A. Thekkath, and Lidong Zhou Microsoft Research Silicon Valley Writers of complex storage applications such as distributed file systems and databases are faced with the challenges of building complex abstractions over simple storage devices like disks. These challenges are exacerbated due to the additional requirements for faulttolerance and scaling. This paper explores the premise that high-level, fault-tolerant abstractions supported directly by the storage infrastructure can ameliorate these problems. We have built a system called Boxwood to explore the feasibility and utility of providing high-level ions or data structures as the fundamental storage infrastructure. Boxwood currently runs on a small cluster machines. The Boxwood abstractions perform very close to the limits imposed by the processor, disk, and the native networking subsystem. Using these abstractions dir...