What Warning and Critical values to use for check_load?

Question

Right now I am using these values:

# y = c * p / 100
# y: nagios value
# c: number of cores
# p: wanted load procent

# 4 cores
# time        5 minutes    10 minutes     15 minutes
# warning:    90%          70%            50%
# critical:   100%         80%            60%
command[check_load]=/usr/local/nagios/libexec/check_load -w 3.6,2.8,2.0 -c 4.0,3.2,2.4

But these values are just picked almost random.

Does anyone have some tested values?

Answer 1

It depends on load the server have, and what load you'd expect.

But start with something in the ranges of

5 min load avg:
w: <ncpu> * 8
c: <ncpu> * 10

10 min load avg:
w: <ncpu> * 5
c: <ncpu> * 8

15 min load avg:
w: <ncpu> * 2
c: <ncpu> * 3

and adjust for each server, so you get notifications when it makes sense for the particular server.

Answer 2

A good complement too Nagios is a tool like Munin or Cacti, they will graph the different kinds of workload your server is experiencing. Be it load_average, cpu usage, disk io or something else.

Using this information it is easier to set good threshold values in Nagios.

Answer 3

Do you know at what load average your system's performance is affected? We had servers at my last job that would consistently sit at 35-40 load average, but were still responsive. It's a measurement you have to do a bit of detective work to get accurate numbers for.

You might want to instead measure some other metrics on the system, like average connect time for SSH or http; this might be a better indicator of how much load your system is under.

Answer 4

Unless the servers in question have an asynchronous workload where queue depth is the important service metric to manage then its honestly not even worth monitoring load average. Its just a distraction from the metrics that matter like service time (service time, and service time).