Disable Spotlight Indexing on a Volume in OS XRevisionas of Sunday, 27 December 2015 at 07:27 UTC

Like a Boss

Let’s say our drive is called (and mounted as) Backup Drive. Open up a
terminal window:

cd "/Volumes/Backup Drive"  
touch .metadata_never_index

Et voila!

Via System Preferences

1. Go to System Preferences → Spotlight → Privacy
2. Drag the volume into the list
3. Ta da!