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QsNet is the main (and only) product of Quadrics, a company that initially started in the 1990s as the British firm Meiko that made parallel systems called the Computer Surface 1 and 2. In the CS-2 a very good logarithmic network was included that was made into a separate product after Meiko closed down and the network part was taken over by the the Italian company Alenia and put in the independent company Quadrics. The success came when Digital/Compaq chose QsNet as the network for its large high-performance computer products, the AlphaServer SC line. Some very large configurations of these machines were sold, e.g., at the Pittsburgh Supercomputing Centre and the French CAE. QsNet proved to be a very fast and reliable network and since about two years QsNet is also offered for cluster systems. Like Infiniband and Myrinet the network has effectively two parts: the ELAN interface cards, comparable to Infiniband Host Bus Adaptors or Myrinet's Lanai interface cards, and the Elite switch, comparable to an Infiniband switch/router or a Myrinet switch. The topology that is used is a (quaternary) fat tree like in most Infiniband switches, see Figure 5b for an example. The ELAN card interfaces with the PCI-X port of a host computer.
Ready-made Elite switches for clusters come in two sizes: with 16 and 128 ports
but nothing in between. Of course one can put together networks for other sizes
but this goes at the cost of compactness and speed. A difference with the other
switches lies in the providing two virtual bi-directional channels per
link. Since the end of 2003 Quadrics sells its second generation QsNet, QsNet
II. The structure, protocols, etc., are very similar to those of the former
QsNet but much faster: where in [33] a
speed of 300 MB/s for an MPI Ping-Pong experiment was measured while QsNet II
has a link speed of 1.3 GB/s. In this case the PCI-X bus speed is a limiting
factor: it allows for somewhat more than about 900 MB/s. However, with the
advent of PCI Express this limitation may be over. Also the latency for short
messages has improved from ≅ 5 µs to close to 1 µs. Like Infiniband, QsNet(II) has RDMA capabilities that allow to write/read from/to remote memory regions on the ELAN cards. This can however be extended to memory regions of the host processor itself. So, in principle, one would be able to view a QsNet-connected system as a virtual shared memory system. As yet, this has not been realised nor on integrated systems, nor on clusters. Nevertheless, it could be an attractive alternative for the much slower memory paged based virtual shared memory systems like ThreadMarks [1]. A Cray-style shmem library is offered that enables one-sided communication via put and get operations as well as an MPI-2 implementation that supports one-sided communication calls. Since early 2006 Quadrics also offers 10 Gbit Ethernet cards and switches under the name QSTenG. These products capitalise on the experience obtained in the development of the two generations of QsNet but they are not meant for inter-processor communication. As yet Quadrics does not seem to consider developing multi-protocol products like Myricom's Myri-10G and Infiniband. |