About Load average in htop, how to decide if it's still doing ok?

Question

I use 'htop' to monitor my web server. It's recently quite loaded and the Load average is showing something like this:

Load average: 3.10 2.56 1.63

I searched the web about these numbers and I found an article about it: http://blog.scoutapp.com/articles/2009/07/31/understanding-load-averages

In the article, it says if I have 2 CPUs, 2.0 means 100% CPU utilization.

And my VPS has two CPUs, so what does 3.1 mean? How could it exceed 100% CPU utilization?

And from these numbers, does it mean I should be wary about the loading now? But the performance seems totally fine, and this is a managed VPS, the hosting company has not notified me any warning about it.

During day time, Load average always show these high numbers... here is another snapshot while writing.

Load average: 3.03 2.77 1.97
Load average: 0.41 1.29 1.60 <---- 5 more minutes later

So I am wondering how much room left for this site to grow in current configurations? What kind of proactive actions I should take in advance?

I don't want to wait until the server bursts.

Thanks.

Solution

Load is just one indication out of many. And load can be high for several reasons.

To know if your server is doing fine it's best to also use monitoring tools such as munin, which gives you nice looking graphs of many different aspects of your system. You might find out that your load is high because the system is swapping a lot. In this case, increase RAM or decrease memory use of applications. Another good thing to check is database performance, you can do that with tools such as mysqltuner.

If you mainly care about server speed pingdom can be a useful online website speed testing tool.

In terms of pro-activity, start measuring more in different way, keep track of what's happening and make sure you can upgrade your VPS on short notice if you're suddenly seeing a lot of extra traffic.