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So I just noticed that if I click on the 'conn' monitor, and then the HISTORY button, all my hosts are showing red on that histogram. Yet everything is fine otherwise. They aren't actually alerting, just the history page.

I think you need to show us the image you're seeing.

The histograms consist of the time-markers (showing the hours, or days, or months) and the color-bar. The time-markers can very well be red without there being a red stripe in the color-bar; that is just an indication that there was an outage e.g. in August, but it was too short to show up as a stripe on the color-bar. (That's what the "Min. duration shown" tells you).

The color bars on all my hosts are showing red since February 15th. And the history list shows all my hosts going red since that date. I wonder if that was the day I installed a new release. But it's weird that only the ping check shows this behaviour.

I'll get a screenshot if that's not clear enough.

-- Bruce Z. Lysik <blysik at shutterfly.com> Operations Engineer