VISA: Netstation's Virtual Internet SCSI Adapter

In this paper we describe the implementation of VISA, our Virtual Internet SCSI Adapter. VISA was built to evaluate the performance impact on the host operating system of using IP to communicate with peripherals, especially storage devices. We have built and benchmarked file systems on VISA-attached emulated disk drives using UDP/IP. By using IP, we expect to take advantage of its scaling characteristics and support for heterogeneous media to build large, long-lived systems. Detailed file system and network CPU utilization and performance data indicate that it is possible for UDP/IP to reach more than 80% of SCSI's maximum throughput without the use of network coprocessors. We conclude that IP is a viable alternative to special-purpose storage network protocols, and presents numerous advantages.