Myrinet

Myrinet, ANSI / VITA 26-1998, a proprietary high-speed local area network system is developed by the company Myricom to create the connection between different machines of a computer cluster. Myrinet has much less protocol control expenses ( overhead ) than other standards such as Ethernet, which allows higher data throughput, less interface cards, and shorter latencies. Although it can also be used as a traditional network system, it is mostly applied directly from the applications, bypassing the operating system.

Myrinet consists physically of two fiber optic cables transmit and receive lines, which are connected using a single connector to the computer. The individual computers are then connected together by means of routers and switches. Myrinet includes a number of provisions for fault tolerance, which are mostly dealt with by the switches. These include flow control, error control and heartbeat monitoring on each connection. The first generation of hardware offered 512 Mbit / s data transmission in both directions, then later versions supported 1.28 Gbit / s and 2 Gb / s The latest "Fourth - generation Myrinet " supports 10 Gb / s and is at the hardware level (physical layer) (cable, connectors, distances, signals) compatible with 10 Gigabit Ethernet.

The data throughput of Myrinet is close to the theoretical maximum of the physical layer. On the 2.0 Gbit / s adapters an actual rate of 1.98 Gbit / s is achieved. The dual -rail cards with two bidirectional links coming to a data rate of 3.95 Gb of / s The latency is for the card with a 333- MHz RISC processor 2.6 microseconds. The fourth generation offers a measured bandwidth of 9.8 Gbit / s When using sockets benchmarks show how netperf a throughput of 9.7 Gbit / s For computer clusters, the low latency is more important than the high data throughput, since according to the law Amdahl'schen the overall performance of a high-performance parallel system is determined by the slowest sequential process, which is usually the signal propagation time over the network.

Myrinet has been more and more displaced by Gigabit Ethernet and Infiniband in recent years. In the TOP 500 list of supercomputers in November 2007 Myrinet only has a share of 3.6 %.