2.6 The Beowulf Network

Early Beowulfs used 10 Mbps Ethernets but the majority today are integrated with 100 Mbps or Fast Ethernet. Greater bandwidth has been achieved both with Myrinet and Gigabit Ethernet at rates approaching 1 Gbps but these are expensive options, costing up to half the total price of a system. In contrast. a Fast Ethernet card costs under $50, and ports cost about $100 each on aggressively priced switches.
The network is medium through which processors communicate. Networks have evolved considerably from the passive multi-drop coaxial Ethernet cables that once connected small numbers of computers. Coax was replaced by active hubs that could connect up to 16 nodes relatively cheaply, but that still broadcast all traffic to all nodes. Switches are more complex, containing logic that identifies the destination of each data packet, and routes the packet to the appropriate port. Thus. each node connected to a switch has the entire bandwidth (100 Mbps) available for its own communication. Switches became cost effective in 1996 and by 1998. switches with 48 ports, each capable of 100 Mbps full duplex (i.e., in both directions at once) were easily affordable. Gigabit Ethernet switches up to twelve ports are available, but still costly. Other products at increased cost per port can support even larger networks. Using a combination of switches and processor nodes for storing, forwarding and routing, much larger configurations can be achieved on the order of a thousand nodes with total latency increase of less than a factor of three.
2.7 Linux
The operating system is the software environment that grants access to the processor and memory, provides services to the application programs, presents an interface to the end user, and manages the external interfaces to devices and the external environment. The most popular operating systems on PCs are sold by Microsoft, but several others exist including Linux, OpenBSD, FreeBSD and several commercial Unix variants. Beowulfs use an open source Unix-like operating system, i.e.. a software system where all source code is freely available and can be studied and improved by the community. Linux, in particular, is the most popular operating system for Beowulfs.
Linux is a monolithic, multitasking, virtual memory, demand paged, POSIX compliant operating system. It is available at no cost over the Internet or at small cost on CD-ROMs. Linux comes with complete source code and is a powerful research tool for computer science. It was for this reason that Linux was selected, even at its earliest stage of evolution, as the basis for the Beowulf project. Linux

 



How to Build a Beowulf
How to Build a Beowulf: A Guide to the Implementation and Application of PC Clusters (Scientific and Engineering Computation)
ISBN: 026269218X
EAN: 2147483647
Year: 1999
Pages: 134

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