ACADEMIA

Microway will exhibit its FasTree modular InfiniBand switch at Supercomputing 2005. The switch will be shown in an Opteron-based cluster using PathScale's InfiniPath-HTX cards, which provide latencies as low as 1.3 microseconds. The FasTree offering is a 36-port DDR switch, based on Mellanox's new InfiniScale III 4X DDR component. Up to this point, all InfiniBand links ran at 2.5 GHz. The new DDR switch uses copper links running at twice this speed, and is the first offering to the HPC community of an InfiniBand switch that uses DDR links. Microway will present a white paper entitled Low Latency Modular Switches for InfiniBand at SC05 on Tuesday at 4:30 PM in the Exhibitor Forum series. It includes a full description of paradigms for connecting FasTree switches, simulations of their performance and MPI benchmarks which demonstrate the benefits of low latency switches for running fine grain parallel problems. It is also available at microway.com. "The main benefits of FasTree technology are its distributed modularity, extremely low latency and extensibility. These features double the size of the three hop fat tree fabrics that can be created with it, while at the same time doubling the size of local low latency domains," commented Stephen Fried, Microway's co-founder and CTO. "The FasTree architecture enables modular extensible fabrics. Users are now free to experiment with different fabric topologies that meet their needs and are either non-blocking or slightly blocked. Simulations show that non-blocking fabrics are often overkill for many MPI applications, increasing latency while at the same time not providing any real bandwidth benefit. Simply stated, because InfiniBand often provides more bandwidth than the typical HPC node or application can use, it often does not pay to use truly non-blocked fabrics. Taking advantage of this extra bandwidth to aggregate nodes into larger local domains provides lower latency communication between nearby nodes, while at the same time making large fabrics possible. It also provides system administrators with an opportunity to aggregate nodes into groups of 24, instead of 12, which keeps users from interfering with each other in clusters that get shared. " Working with PathScale's InfiniPath Opteron HTX Adapters, the number of hops required to move MPI messages between nodes is reduced, which significantly reduces fabric latency. "The Microway FasTree switch is an innovative design that our PathScale InfiniPath customers will find extremely cost-effective," stated Len Rosenthal, Vice President of marketing for PathScale. "The combination of the industry's lowest latency cluster interconnect, the PathScale InfiniPath HTX InfiniBand Adapter, and Microway's FasTree switch will make the clear performance advantages of InfiniBand more affordable to all HPC users." The switches also have long-term economic benefits. An interesting characteristic of InfiniBand switches is that different speeds and widths work together. Therefore, current SDR/DDR 4X models will be usable as data aggregation devices when QDR technology becomes available in coming years. The switches were also designed from the ground up to be modular. As a result, the user doesn't have to purchase a 96 or 144 port switch to build a 32, 48 or 64 port cluster! In addition, the cabling problem that results when all of the cables in a cluster come together at a single point can be eliminated, by simply distributing the switches with the cluster nodes. The FasTree architecture also results in switch fabrics that are extensible and can be used in basic research in network design. As a user's need grows, he or she can change the topology to match the cluster resources currently owned, adding switches and changing topologies with time, to accommodate increasingly larger clusters sizes.