VideoOne challenge facing commercial P2P brokers, which will haunt commercial applications of the Grid as well, is philanthropy. In April, Intel launched a philanthropic peer-to-peer program that lets PC owners give their excess processor time to a good cause. The first software package that can be downloaded under this program, developed by United Devices in collaboration with a consortium of cancer research centres, is aimed at optimising the molecular structure of possible drugs for fighting leukaemia. While this may be good promotion for United Devices, it remains to be seen how many of these brokerage firms can turn a profit.
Safety in Numbers
If the P2P data-processing paradigm is the equivalent of assembling a ragtag army of poorly trained conscripts, the other end of the computing spectrum is a commando unit made up of a tightly knit set of PCs dedicated to solving a single problem. One of the pioneering efforts in this field was called Beowulf, after the hero of the legendary poem who slays two man-eating monsters. The original Beowulf, built in 1994 by Thomas Sterling and Don Becker at the United Space Research Association in Maryland, was a cluster of 16 off-the-shelf processors lined together by Ethernet cables. Its success inspired many others to build quick-and-dirty number crunchers out of cheap components — thus slaying the twin monsters of supercomputing, time and money.
Beowulf's success depended not so much on the architecture of the computer — many commercial supercomputers are based on large arrays of fairly standard processors — but more on the price/performance ratio of the network technology. Supercomputers require proprietary "glue" to link their processors together, and this is both expensive and time-consuming to develop. Beowulf-like systems tend to use fast but affordable Ethernet technology. Some of Beowulf's offspring, referred to as "commodity clusters", now rank among the top 50 of the world's fastest supercomputers — offering speeds up to 30 teraflops per second. They can often cost less than a hundredth of the price of an equivalent supercomputer. Cluster construction, which started as a nerdy hobby, is now a mature industry with turnkey solutions offered by manufacturers such as Compaq and Dell.
The intellectual link between Beowulf and the Grid is that, as transmission speeds on the Internet increase, clusters no longer need to be in the same room, the same building, or even the same country. In some sense, this is old news. A software system called Condor, devised by Miron Livny and colleagues at the University of Wisconsin in Madison during the 1980s, combined the computing power of workstations in university departments. With a Condor system, researchers can access the equivalent of a cluster of several hundred computers.
In a similar way, a number of European supercomputer facilities were linked together in the late 1990s as part of a project called Unicore that was run by a German research consortium. Using Unicore software, users can submit huge number-crunching problems without having to worry about what operating software, storage systems or administrative policies will be used on the machines that do the work.
Between them, SETI@home, Beowulf, Condor and Unicore all contain elements of what the Grid's visionaries are after: massive processing resources linked together by clever software, so that, from a user's perspective, the whole network melds into one giant computer. To emphasise this, the latest extension of the Unicore project has been dubbed E-Grid. To purists, however, this is only the beginning. They believe that Grid technology should blur the distinction between armies of individual P2P computers, dedicated commodity clusters, and loose supercomputer networks. Ultimately, a PC user linked to the Grid should not need to know anything about how or where the data are being processed — just as a person using a toaster does not need to know whether the electricity is coming from a wind farm, a hydroelectric dam or a nuclear power plant.
The Missing Link
Piecemeal solutions to building such a Grid are already at hand. A layer of software, called "middleware", is used to describe the kind of tools needed to extract processing power from different computers on the Internet without any fuss. The most popular middleware so far is the Globus tool-kit developed by Mr Foster's group at Argonne, in collaboration with Carl Kesselman's team at the University of Southern California in Los Angeles.
The tool-kit contains programs such as GRAM (Globus Resource Allocation Manager), which figures out how to convert a request for resources into commands that local computers can understand. Another tool is called GSI (Grid Security Infrastructure) which provides authentication of the user, and works out that person's access rights. One of the attractions of the Globus toolkit is that such tools can be introduced one at a time, and often painlessly, into existing software programs to make them increasingly "Grid-enabled". Also, like the World Wide Web and the Linux operating system, the creators of the Globus toolkit are making the software available under an "open-source" licensing agreement. This allows others to use the software freely, and add any improvements they make to it. One example is Condor-G, an improved version of the Condor program that deals with the security and resource-management problems that occur when Condor is extended over institutional boundaries.
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