I voted for Nagios, as I have it set up & running flawlessly. Very stable, easy to set up etc.

Zabbix would be my second choice, as it has some very nice features, but I need more experience with it.

Cacti should be included next year...

Wheres Icinga??

OpenNMS comes in at #2. Interesting.

Wow ! Nagios first !

Nagios winning is no surprise given that even Linux magazines publish articles about it. Perhaps a more interesting poll would be who is paying for monitoring: either licenses (for tools with commercial editions) or for support (for the free versions).

i.e. "What solution is valuable enough to pay for?" - that's a much harder question to answer... maybe options like GroundWork would rank higher?

Nimsoft is the best of them all, the fastest to deploy and support RISC based cpu's on AIX and Redhat. Also the only one I know of that can monitor LPAR's disk I/O on PowerVM as the HyperVisor. Low cost, secure, one stop shop dashboards that support integrations with Nagio's and any other monitoring application, is full cloud enabled and was recently aquired by CA during the same week as 3Terra the next Amazon of cloud providers. Nimsoft was a private held company whose growth has doubled since 2004 and was cash sustained unlike other companies these days, ressession and all. I am all for OpenSource 99% of the time but when I seen the demo of this thing and every question I answered was not only a yes but when I seen who easy it was to plan and deploy a platform agnostic solution that sold it for me. I don't know about a lot of you in here but I support all platforms of Unix, Linux, Apple/MacOS, Windows for the last 21 years and develop in many languages. The biggest pain for support is trying to get open source applications which were intended to only run on Linux working in Windows, but these days it's getting a lot better.

Check out Nimsoft, I am sure everyone will love it but will hate the fact they are not open source, though they are agentless, and can monitor every server and device on your network, the pricing is per hardware device so there is value there since one physical server could host 10 virtuals and that counts as one license.

Nagios, nimsoft and groundwork.

nagios and ganglia

I swear by Zenoss Core. Running 13 production servers on it right now with many more to come. Tons of community driven development and support is available at http://community.zenoss.org and on IRC at irc.freenode.net - #zenoss.

Zenoss fully replaces Nagios and Cacti, it's basically both of those wrapped in to one with even more features (and a much nicer interface which is getting completely revamped to look/function even better for the next release).

I don't know if anyone's heard of it yet, but Circonus (http://circonus.com/) is pretty effing cool. They're a little different in that they stress metric collection over "uptime" or other abstracted value. But it's like Cacti/Ganglia on steroids. Once you've started collecting data, creating (and re-creating) graphs is incredibly easy. Graphs are effectively collections of metadata rather than one-time files like rrd-based systems. And all metrics can have rules applied to them for notifications.

Because it's not free, it probably won't win any contests like this. But it's a hell of a lot easier (and effective) to use than anything else I've seen.

nagios Nagios NAgios NAGios NAGIOs NAGIOS!!!!!