Failure-Atomic File Access in an Interposed Network Storage System

This paper presents a recovery protocol for block I/O operations in Slice, a storage system architecture for highspeed LANs incorporating network-attached block storage. The goal of the Slice architecture is to provide a network file service with scalable bandwidth and capacity while preserving compatibility with off-the-shelf clients and file server appliances. The Slice prototype “virtualizes” the Network File System (NFS) protocol by interposing a request switching filter at the client’s interface to the network storage system (e.g., in a network adapter or switch). The distributed Slice architecture separates functions typically combined in central file servers, introducing new challenges for failure atomicity. This paper presents a protocol for atomic file operations and recovery in the Slice architecture, and related support for reliable file storage using mirrored striping. Experimental results from the Slice prototype show that the protocol has low cost in the common case, allowing the system to deliver client file access bandwidths approaching gigabit-per-second network speeds.