I am leasing a virtual private server with 1 gig of memory and 3 IP's. This is a CentOS linux server with apache and MYSQL. I'am running 3 vbulletin forums, 1 SMF forum, and 5 wordpress sites. Just about all of my sites (6 or 7) are on 1 ip address. Can this affect the performance of the server? Does it really matter how many sites are on 1 IP address? Or should I spread the sites around to the other 2 addresses? So lets say that I have 6 sites and 3 IP's. Should there be 2 sites per IP address? Or does it really matter?
The sever is what is going to affect performance, not the IP address. There can be thousands of sites on the same ip.
A shared IP doesn't affect in terms of server performance. If you need to configure SSL for example then you'll need a dedicated IP for that specific domain.
Depends on how much resources each of your sites use. But the IP address should not affect performance.
For the amount of sites you are running it wont affect it, depending on the specs of the server. But once the sites start generating a lot of traffic, then you will start to experience drop in bandwidth (depends on the speed of the line).