I want to try the Catalina beta without messing up my primary drive. - I got a Samsung X5 external ssd. Performance is actually better then the internal on my new Mac mini - I cloned my drive to the SSD, booted off it. When running on the external SSD it's unusable slow. A lot of beachball. Opening an app can take minutes, etc. If I reformat the external drive & use it for data, I'm getting 1800MB write 2500MB read speeds. So I know the external drive is flying. Anyone see an issue like this or have any ideas?