apache – Avoiding copying all the files again!

I have a server with 400 GB of data, only webmasters have access to these files.
There is a login system that allows only these members to display these files.
Now there is another group of people who must access half of these files, not all of them.
My problem is: there is no option to hide files.
So the only way is to copy files from group 1 to a new directory for group 2, but that will use a lot of space and make the server heavier.

Is there any way to avoid copying all these files again?

Note: the server is apache, and the system design in PHP and MySQL