Question: How much memory will I need to run virtual machines on my server?
Answer: There is no simple answer to this question. Generally speaking, to virtualize an operating system you need at least as much RAM as is normally required to run the OS independently. Therefore, if your OS requires 512MB of RAM to run normally, it will require that in virtualization.
It is, however, not quite that simple. Depending on your application needs, server loads, and the amount of data being accessed and transferred, your needs could range from the low (512MB) to the high (4GB) or even beyond that.
Therefore, it is important to know exactly what you need and how much RAM you would normally need to run the applications you are trying to run. Some virtualization software also includes dynamic memory allocation so that you can set a base amount and allow the amount used to expand on an as-needed basis. As with anything that might tax your server’s load, use it wisely.