Now that you know how to SSH into your server it is important to familiarize yourself with some basic command line tools.
We often get calls and tickets from VPS and dedicated customers wondering why, when their server is largely idle, much of their RAM appears to be in use.
When RAM is not needed for other functions, your server will load frequently-accessed files into memory in order to read them more quickly. When a file is loaded into RAM, the server can access the information orders of magnitude faster than from disk. A current SATA disk can read files at 100 MB/second, if the files are in sequential units. However, RAM can be read at GB/second, or even tens of GB/second rates.