So, I'm currently on a VPSVille Cpanel3 account that has 768 MB guaranteed ram and 2048 MB burst ram (full details here: http://www.vpsville.ca/cpanel-vps). It's running CentOS, Cpanel, Apache and FastCGI.
On the server itself I have a Joomla community site with a forum system that generally has about 20 people on it max at any point and even then, during the evening, no one. It's a pretty small site but has a number of modules running on it. It gets about 6000 visits a month. Also on the server is a WordPress site that gets about 80-150 visits a day, 2 other WordPress sites that aren't developed yet so they don't get any traffic at all, and 2 static HTML websites that also only get about 500 hits a month. All in all, no huge sites.
The issue is that I get "out of memory" errors fairly frequently and it kills my server and I need to reboot it in order to get all my sites up and running again. It seems to me that I shouldn't have these issues with that much RAM allotted to my account. Every time I send in a support ticket, they just tell me to upgrade the RAM.
Now, I'm still pretty new to all this, so I'm not a good judge of how much I really need for my sites to run. I don't know if my sites really do need this much or if VPSVille has oversold their servers, they don't actually have those resources available and I'm getting ripped off.
So, how much RAM should I be using with my current setup?