I am looking for a simple tool or service to track the server-side performance of a website over time.
It would be nice to have the possibility to register a set of URLs for different page types and see graphs how response/download time goes up or down over time.
This might either be a tool to install on a server of our own, our a service. Of course, free of cost would be preferred, commercial solutions should be a lot cheaper than what I saw so far (50$/month is definitely far too much to spend for something like this)
I know that the G-Webmaster tools offer a graph for average download time, but the problem lies in "average". If a single page type is slowed down for some reason, it does not hit the average enough that the issue can be quickly detected.
Thanks a lot for your suggestions, Peter
EDIT: currently I am running linux servers, but I might be able to set up a windows machine for this, too. So software for both OSs would be interesting. (OS independency would be appreciated, though :)