Myrinet
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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 Gbit/s. Newest "Fourth-generation Myrinet" supports 10 Gbit/s data rate, and is interoperable with 10 Gigabit Ethernet on PHY, the physical layer (cables, connectors, distances, signaling). According to Myricom Fourth-generation Myrinet products are expected to start to ship in September 2005.
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 embarrassingly parallel supercomputer workloads.
According to Myricom, 141 (28.2%) of the June-2005 TOP500 supercomputers use Myrinet technology, making it the most popular. [1]
In the November 2005 TOP500, the number of supercomputers using Myrinet is down to 101 computers, or 20.2%. [2]
The June 2006 list reports 87 Myrinet machines, and the November 2006 one 79 (15.8%).
