Quote Originally Posted by Gilben View Post
True. Don't delete it, copy the entire directory on an external HDD to be sure and only after that install the DX11 client.
Ok I still don't think people are understanding this so let me try to elaborate.

Your FFXIV game at this time is about 14.5 GB in data. Of this 14.5GB, about 17MB is the actual client. The other 14,483 MB is the assets, which include textures, sounds, scripts, icons, and all other data needed to create FFXIV. When you start FFXIV, you open the launcher (patcher) which checks to see if you need to patch. The launcher then starts the client.

In the DX11 model, nothing is changed except we get a second client, and you pick which one you run through the launcher. Downloading the DX11 client doesnt force you to re-download the entire game, nor does it delete the old client, it simple adds another executable file to your system, so like others have stated, probably like 25 MB judging from the HW benchmark.