Darrell C. Anderson

Interposed request routing for scalable network storage

This paper explores interposed request routing in Slice, a new storage system architecture for high-speed networks incorporating network-attached block storage. Slice interposes a request switching filter - called a µproxy - along each clients network path to the storage service (e.g., in a network adapter or switch). The µproxy intercepts request traffic and distributes it across a server ensemble. We propose request routing schemes for I/O and file service traffic, and explore their effect on service structure. The Slice prototype uses a packet filter µproxy to virtualize the standard Network File System (NFS) protocol, presenting to NFS clients a unified shared file volume with scalable bandwidth and capacity. Experimental results from the industry-standard SPECsfs97 workload demonstrate that the architecture enables construction of powerful network-attached storage services by aggregating cost-effective components on a switched Gigabit Ethernet LAN.

SmartBridge: a scalable bridge architecture

As the number of hosts attached to a network increases beyond what can be connected by a single local area network (LAN), forwarding packets between hosts on different LANs becomes an issue. Two common solutions to the forwarding problem are IP routing and spanning tree bridging. IP routing scales well, but imposes the administrative burden of managing subnets and assigning addresses. Spanning tree bridging, in contrast, requires no administration, but often does not perform well in a large network, because too much traffic must detour toward the root of the spanning tree, wasting link bandwidth.

A case for buffer servers

Faster networks and cheaper storage have brought us to a point where I/O caching servers have an important role in the design of scalable, high-performance file systems. These intermediary I/O servers-or buffer servers-can be deployed at strategic points in the network, interposed between clients and data sources such as standard file servers, Internet data servers and tertiary storage. Their purpose is to provide a fast and incrementally scalable I/O service throughout the network while reducing and smoothing demands on shared data servers and the network backbone. This paper outlines a case for caching buffer servers and addresses some of the key technical challenges in the design of a buffer service. We also describe the role of buffer servers in the Trapeze project, which uses Gbit/s networks as a vehicle for high-speed network I/O.

Failure-Atomic File Access in the Slice Interposed Network Storage System

This paper presents a recovery protocol for block I/O operations in Slice, a storage system architecture for high-speed 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 clients interface to the network storage system. 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.