Myrinet, ANSI/VITA 26-1998, is a high-speed local area networking system designed by Myricom to be used as an interconnect between multiple machines to form computer clusters. Myrinet has much less protocol overhead than standards such as Ethernet, and therefore provides better throughput, less interference, and less latency while using the host CPU. Although it can be used as a traditional networking system, Myrinet is often used directly by programs that "know" about it, thereby bypassing a call into the operating system.
Myrinet physically consists of two fibre optic cables, upstream and downstream, connected to the host computers with a single connector. Machines are connected via low-overhead routers and switches, as opposed to connecting one machine directly to another. Myrinet includes a number of fault-tolerance features, mostly backed by the switches. These include flow control, error control, and "heartbeat" monitoring on every link. The first generation provided 512 Mbit/s data rates in both directions, and later versions supported 1.28 Gbit/s and 2 Gbit/s.
Myrinet's throughput is close to the theoretical maximum of the physical layer. On the latest 2.0 Gbit/s links Myrinet often runs at 1.98 Gbit/s of sustained throughput, considerably better than what Ethernet offers, which varies from 0.6 and 1.9 Gbit/s depending on load. However, for supercomputing, the low latency of Myrinet is even more important than its throughput performance, since, according to Amdahl's law, a high-performance parallel system tends to be bottlenecked by its slowest sequential process, which is often the latency of transmission of messages across the network in all but the most embarassingly parallel supercomputer workloads.
According to Myricom, 193 (38.6%) of the November-2004 TOP500 supercomputers use Myrinet technology, making it the most popular. [1]
See also
- HIPPI
- Scalable Computer Interconnect (SCI)
External links
Last updated: 10-08-2005 03:56:17
