26-02-2011, 03:35 PM
12885391-Cluster-Computing.doc (Size: 88 KB / Downloads: 130)
What are clusters?
A cluster is a type of parallel or distributed processing system, which consists of a collection of interconnected stand-alone computers co - operatively working together as a single, integrated computing resource.
This cluster of computers shares common network characteristics like the same namespace and it is available to other computers on the network as a single resource. These computers are linked together using high-speed network interfaces between themselves and the actual binding together of the all the individual computers in the cluster is performed by the operating system and the software used.
MOTIVATION FOR CLUSTERING
High cost of ‘traditional’ High Performance Computing.
Clustering using Commercial Off The Shelf (COTS) is way cheaper than buying specialized machines for computing. Cluster computing has emerged as a result of the convergence of several trends, including the availability of inexpensive high performance microprocessors and high-speed networks, and the development of standard software tools for high performance distributed computing.
Increased need for High Performance Computing
As processing power becomes available, applications which require enormous amount of processing, like weather modeling are becoming more common place requiring the high performance computing provided by Clusters
Thus the viable alternative to this problem is
“Building Your Own Cluster”, which is what Cluster Computing is all about.
Components of a Cluster
The main components of a cluster are the Personal Computer and the interconnection network. The computer can be built out of Commercial off the shelf components (COTS) and is available economically.
The interconnection network can be either an ATM ring (Asynchronous Transfer Mode), which guarantees a fast and effective connection, or a Fast Ethernet connection, which is commonly available now. Gigabit Ethernet which provides speeds up to 1000Mbps,or Myrinet a commercial interconnection network with high speed and reduced latency are viable options.
But for high-end scientific clustering, there are a variety of network interface cards designed specifically for clustering.
Those include Myricom's Myrinet, Giganet's cLAN and the IEEE 1596 standard Scalable Coherent Interface (SCI). Those cards' function is not only to provide high bandwidth between the nodes of the cluster but also to reduce the latency (the time it takes to send messages). Those latencies are crucial to exchanging state information between the nodes to keep their operations synchronized.
INTERCONNECTION NETWORKS
Myricom
Myricom offers cards and switches that interconnect at speeds of up to 1.28 Gbps in each direction. The cards come in two different forms, copper-based and optical. The copper version for LANs can communicate at full speed at a distance of 10 feet but can operate at half that speed at distances of up to 60 feet. Myrinet on fiber can operate at full speed up to 6.25 miles on single-mode fiber, or about 340 feet on multimode fiber. Myrinet offers only direct point-to-point, hub-based, or switch-based network configurations, but it is not limited in the number of switch fabrics that can be connected together. Adding switch fabrics simply increases the latency between nodes. The average latency between two directly connected nodes is 5 to 18 microseconds, a magnitude or more faster than Ethernet.
Giganet
Giganet is the first vendor of Virtual Interface (VI) architecture cards for the Linux platform, in their cLAN cards and switches. The VI architecture is a platform-neutral software and hardware system that Intel has been promoting to create clusters. It uses its own network communications protocol rather than IP to exchange data directly between the servers, and it is not intended to be a WAN routable system. The future of VI now lies in the ongoing work of the System I/O Group, which in itself is a merger of the Next-Generation I/O group led by Intel, and the Future I/O Group led by IBM and Compaq. Giganet's products can currently offer 1 Gbps unidirectional communications between the nodes at minimum latencies of 7 microseconds.