Minecraft Lag Problems?

My server is having lag problems all of the sudden. I am pretty sure that it is one of the plugins. What is the best way to find out which plugin is the one responsible. I can't just slowly remove the plugins, that would take too long and my server is 24/7. I have heard of speed tests, but I don't know how to do that either. I can't take the server down for very long, maybe an hour or two at a time. Please help.

 

Bump

 

It would be nice to see wich plugins you have.
Edit:
some plugins are bigger than others, so that's why i want to know wich u have.

 

BobTheHunted Please follow these instructions so we can help you.

 

Jocke155 I just took a screenshot: https://www.dropbox.com/s/lx1brzuwq9axh2k/2013-08-11_19.26.56.png

 

How large is your map? How many concurrent worlds do you have active at any time? What's your average TPS? Have you installed any new plugins recently?

 

DinoThrone My map is fairly large, but not large enough to cause any lag when no players are online. I have around 4 worlds, only two active, one nether, and one the main world. How do I get my average tps?

And it might be important to mention the lag didn't exist before any 1.6.- build.

 

Well, that's maybe the problem then. Always when a new dev-build, or beta build releases, they are really laggy for some reason, i got MUCH more MS when i use dev and beta-builds.

But when a recommended build releases, the ms is lower again.
Also, the world can make problems, when i use multiply worlds on my server i get much more lag.

 

Jocke155 Thanks for the info, it looks like the beta build just came out too, so I will try that