I have a VPS account from knownhost. I have clients who have their website hosting on my server.
Some have subscribed 50MB, 100MB, 500MB or 1 GB as per their requirement. They are also allowed to create email address in their accounts but the email address's capacity will be shared with web site's space.
Now I would like to separate that web hosting space and email account's space.
So What is it called and from where can i start?