Could my spotlight search index have really been 2.5 GB on a 256 GB drive? I have a MacBook Air (13-inch, Mid 2012) with El Capitan 10.11.6 and a 256 GB SSHD. I was having fan/CPU usage issues with mds and using the lines in this answer turned it off and deleted the index.

sudo mdutil -a -i off

sudo rm -rf /.Spotlight-V100/*


It's quiet now, and cool as a cucumber. But I was surprised to see 2.5 GB of hard drive space freed up at the moment I deleted the index.

My 256 GB drive is fairly full, so that's about 1%. Does that sound right? About 1% of the size of my stuff is used for indexing? Just curious.

I have quite a mix of file types, years of photos, lots of text and pdf's for research, youtube downloads, python's numpy and other text and non-text data files... does it all somehow get indexed?  

Is there some magic way to stop it from opening file types I'm not interested in indexing?



This is the "before" situation. All is quiet now that indexing is turned off.
All that you write sounds perfectly normal to me.


  
    does it all somehow get indexed?
  


Yes it does.


  
    Is there some magic way to stop it from opening file types I'm not interested in indexing?
  


Well, not directly. But you can exclude folders, by either adding .noindex to the folder name, or by going into System Preferences → Spotlight → Privacy. You may want to move all the files you don’t want indexed into such a location.

Also see How can I make spotlight ignore certain file types and directories? As far as I know there’s no way to tell Spotlight NOT to index certain file types.