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Munin doesn't scale by default.

Just started playing with Munin as a potentially better option than Cacti (hard to automate) for trending. I have about 30 hosts being watched by munin. The munin update job (which fetches and regenerates graphs, etc), by default, runs every 5 minutes. It takes almost 4 minutes to run on a 2.5gHz host. If we add any more things to monitor it's likely that we'll soon overrun the 5 minute interval.

Examining the process, it looks like most of the time is spent generating graphs. Every graph displayed on the munin webpages is regenerated every 5 minutes whether or not anyone looks at the graphs. This can't scale.

There is an option you can give in your munin.conf:

graph_strategy cgi
This, and a few other changes, will make munin skip the graph prerendering. If I set the graph_strategy to cgi, the runtime drops to 28 seconds, most of which is spent generating the static HTML for the munin web interface - even if no one looks at it.

Really, though, this is 2009: static html, really? Sarcasm aside, dynamic generate-on-the-fly webpages are basically the standard these days. Munin needs a better frontend that isn't static HTML.

Among other oddities, it doesn't seem like you can time travel. Your default graph options are today, this week, this month, this year. Sometimes yesterday, last week, last month, etc, are useful, not to mention the other odd views like 36 hour, 6 hour, etc.