Nagios is a great tool, especially for free.
Find your config
find / -name nagios.cfg
Test nagios against that config (below is where my nagios.cfg was located but change to where yours is)
nagios -v /etc/nagios/nagios.cfg
When your system is checking processes on a system and shows RSZDT and you are wondering what that means.
R = running,
S = interruptible sleep (waiting to complete),
Z = defunct ("zombie") process,
D = uninterruptible sleep,
T = stopped.
Perhaps this is on the cluster (total) -- how many servers is it checking, unless it's on a single system (in which case there may be a problem).
Find what plugins are installed