When I was active in Indyahozting, I was too much worried about server loads. Because it was something that affected all clients, and I hated it when servers crossed a total usage of 75%, which would make all sites on the server slow. There were not much of a problem on the Linux servers, but Windows servers always used to give me a hard time.
Right now, Im in a quest to make all my automated blogs work in full effecienty. I was hosting them on a shared hosting account, but now I have taken a dedicated server from iweb where all those blogs are hosted. And I am amusing myself in finding that the server is running at full effecienty, and that all the pho sites are always busy updating the blogs with articles round the clock, and serving the search engine visitors. The network lines are always busy, and the server’s processor is always at about 90%, and the memory usage is at 1.8 gb out of the 2 GB that it has got.
I dont believe in loading the hard disk though, since that would naturally slow down the server with lots of data. So I have dedicated one disk for the databases alone, and one for the files and logs and stuff. All of them are wordpress sites, and wordpress sites only work with databases a lot, so the 2nd hard drive for sure is getting a lot of work for itself. And a backup of the 2nd drive is constantly being taken in the first drive.
I am worried only about the databases since the php is the same for all the 85 sites that the server hosts, and they all use the very same wordpress templates. So if that is lost nothing is lost. If the databases are lost something is lost, and never is everything lost, since all the site sites that are hosted on the server are automated and get updated by themselves.