You get up in the morning and drive your car to work. Normally you don't pay special attention to the roads, streetlights, stop signs, car engine, or buildings. They're just there. However, consider the difficulty of driving to work if there were no roads, or maybe there are roads but no stoplights and other traffic controls. A nightmare scenario, wouldn't you say? This chapter takes the standard drive to work in the morning and exposes the critical infrastructure of the traffic control system and roads. The Internode Communication Services (ICS the roads upon which cluster communication travels), Distributed Lock Manager (DLM the traffic controls), Kernel Group Services (KGS providing for car pool membership and decisions during cluster communication), and the Reliable Datagram (RDG providing messaging between applications on a cluster horn honking and turn signals) mechanisms are described in this chapter. We also look at the Cluster Mount Subsystem (CMS) and the Token subsystem to round out our discussion of miscellaneous subsystems.

These components are essential to the lower level functioning of the cluster, and these miscellaneous subsystems provide the critical infrastructure for all the components discussed previously in this book.