This small article will provide you with short but in-depth description of the MMM cluster internals, will show you how it's functioning, etc.
Basically, MMM consists of three main parts (scripts):
mmmd_mon - monitoring script which does all monitoring work and makes all decisions about roles moving and so on.
mmmd_agent - remote servers management agent script, which provides monitoring node with simple set of remote services to make servers management easier, more flexible abd highly portable.
mmm_control - simple script dedicated to management of the mmmd_mon processes by commands.