  The latest implementations of commercial UNIX to offer mainframe style
capacity management on enterprise servers include: AIX Workload Manager (WLM),
HP-UX Process Resource Manager (PRM), Solaris Resource Manager (SRM), as well
as SGI and Compaq. The ability to manage server capacity is achieved by making
significant modifications to the standard UNIX operating system so that
processes are inherently tied to specific users. Those users, in turn, are
granted only a certain fraction of system resources. Resource usage is
monitored and compared with each users grant to ensure that the assigned
entitlement constraints are met. In this paper, we begin by clearing up some of
the confusion that has surrounded the motivation and the terminology behind the
new technology. The common theme across each of the commercial implementations
is the introduction of the fair-share scheduler. After reviewing some potential
performance pitfalls, we present capacity planning guidelines for migrating to
automated UNIX resource management.
