cgrafx wrote:Schorsch wrote:cgrafx wrote:Not sure what they mean by lots of extra space.. the system folder only takes up about 6.5 gigs. I wouldn't exactly call that huge.
Correct for the operating system itself, but you also have to install the software you want to use in Catalina again, which takes additional storage space if you don't integrate the "old" volume into Catalina and point to the programs folder on this "old" volume. Same for user data ifn this is located on the "old" volume.
Not sure what you mean by point the programs folder on the old volume. Mac programs do not have a registry like windows does and in most cases can run from any location. There are a few that have license servers that might have to be re-authorized, but for the most part you wouldn't have to do anything more than boot up with the version of the OS you want to use.
If you really want to keep things separate than yes you would need to duplicate your Applications Folder, but terabyte drives are cheap.
Installing the newer OS on what amounts to a separate logical partition will also install an entirely new Applications folder with the new versions, and require reinstalling all authorisations and third-party software over again.