Memory usage: 827.4 MB of 1010.6 MB used; 183.2 MB available CPU usage Last 1 minute 0.00 Last 5 minutes 0.01 Last 15 minutes 0.00 No visitors, why so much memory are used?
I went through this the other day with my server - Linux will utilize free memory if nothing is going on. The thing you need to keep an eye on is load, and SWAP memory usage. If those are high, something's wrong (or traffic is putting a lot of stress on the server).