>>>I know the guys are renting it for a number of years, even before cloud became an IT buzzword. "Co-hosted" or something was the buzzword then.
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>>Maybe colocated? That would mean their own server(s), but on the premises of a 3rd party.
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>Never bothered to learn the difference :).
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>>If that's the case I'd expect your results to be more deterministic, unless you know it's busier with other stuff at certain times of the day.
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>I think that's the cause - the time of day matters a lot. Probably the number of users varies, and who knows what they may be doing, hence the variation.

Bandwidth can be the culprit also when time-of-day matters.