Mac has missing disk space after upgrading to mac OS High Sierra
A macOS High Sierra problem some people have reported encountering is that after the upgrade they have noticed their hard drives are showing a lot less free space than before.
Some users have identified the '/.MobileBackups ' folder as being the culprit. This is a folder that is no longer used in High Sierra, but it can use up a lot of space. Thankfully, it can be removed without causing any issues. First, open up the Terminal and type in:
sudo mv /.MobileBackups ~/Desktop/temp/
This will move the MobileBackups folder to your desktop. Now, drag and drop the folder into your Trash, then empty it. You should now find you have a lot more disk space available.