2.8 Message Passing for Interprocessor Communication

		MPI programs can be written using only six basic primitives. While not restricted to MPI, Beowulf programmers often rely heavily upon this set of tools.

		2.9 Beowulf System Management

		Merely assembling a collection of PCs is not sufficient to create a usable parallel cluster. General system design questions need to be addressed before assembling the cluster, some of which include:

		how the system is to be connected to external networks,

		how IP addresses are assigned to the individual nodes,

		how the file system is to be configured, and

		what security measures are required.

		Once a system is operational, practical means for managing accounts is required. Is a directory system such as NIS appropriate, or should password files be distributed to each of the nodes? Similarly, the allocation and placement of software must be determined. You also have to consider where you want to install system software. Is it sufficient to make all software available via a network file system, or should some of it be installed locally on each node? How is all the software synchronized across nodes? Depending on how the system is to be used, access may have to be limited to parts of the system at different times so that certain users may run their applications undisturbed. Management of system resources is not a simple business.

		Most Beowulf systems incorporate between 8 and 32 nodes and dedicate themselves to servicing a small group of users. These systems do not require as much administration as larger systems. Hardware and software problems are less frequent, and the machines are not generally pushed to their limits by users. Nonetheless, file system setup, software installation, and node configuration are vital tasks.

		2.10 The Beowulf Challenge

		Beowulf-class computing is a rapidly evolving domain of parallel computing with many installations and accomplishments but with much remaining to be done. Furthermore, Beowulfs present a very different business model to the user than conventional commercial offerings. Hardware and software upgrades are managed