But High Sierra won’t let me upgrade it. Anthony KarczI've got 2TB of super-fast storage right there, currently housing my macOS Sierra installation, and it might as well be in another time zone. Their take on macOS High Sierra was that "some developers have gotten word that Apple prevented High Sierra from being installed on a RAID set" but that "installing on a RAID set is only an issue during the install." Once you have High Sierra installed, you'll be able to access your RAID set again. The problem, then, is how to get the latest version of macOS installed in the first place.

Source: Forbes September 28, 2017 15:56 UTC