Is 40 gb disk space enough if I have files of 15 gb.I wont be adding any new few files. I will be creating only sites and discussion. Will it cause any performance issue if the files are stored in the same location as the installation path. What happens in the long run?
If you are creating 15 GB worth of files and those files will never be versioned or changed in any way then the only overhead you'll have is on the Lucene index. That can vary so the best thing to do would be to try it out. 15 GB is not a lot so it shouldn't take that long to test.