I see no reason to have a ram disk of any kind if you are using the 3gb ram VPS for your MySQL server.

You could easily run with that server even if your site's DB grew to 5gb.

You just need to edit the configuration correctly for your server and also do a correct setup by looking into optimizations.

A ram disk for MySQL is the worst idea to ever use even a solid state drive is a very bad idea. This coming from a host is very sad.

Do not try that unless you plan to destroy your database within 5-6 months if your traffic is more then 1k daily.