Load HDD install into RAM

I was just wondering if it was possible to load the installed OS into RAM to improve performance. Is there a way to do this? I looked at an old forum post on this, but it was out of date and the information was not useful (http://forum.alpinelinux.org/forum/general-discussion/running-alpine-ram-installed-hard-drive). I don't care if I have to do a diskless install, but I'd prefer to have it load an installed OS into RAM.