The hardware configuration of the hosting server where you host your sites is really important and can influence their performance. Since a site includes also databases, logs, a Control Panel to handle the content, an email service, etc, you need appropriate hardware that will support these processes. A unit with a high CPU speed indicates that your web apps will be executed much more quickly, while extra physical memory will enable extra system processes to run concurrently, therefore the hardware shall have direct impact on how your websites perform and in the event that the server isn't powerful enough, they will function slowly or will not work at all. In this light, it's essential to check not just what functions a particular hosting plan includes, but also if the hardware will be good enough to support these functions.