I've bought a Samsung T5 500GB to give back some speed to my late 2013 iMac. I erased the SDD (Journaled, GUID), downloaded the installer for Catalina. The installer starts but when it reaches the point to restart the Machine to install Catalina on the external Drive it restarts, but boots right back up from the internal drive. No OS installed on the SSD.
What am i doing wrong?
iMac 27″, macOS 10.15
It worked! The only thing i changed was the USB Port. It was plugged into the last port and i changed it to the first. Before, a card reader was plugged into the first port, but without a card inserted. Now i don't know what really happens, but MAYBE the Mac checks each USB port in (1,2,3,4) order on startup, and it somehow took too long for a response of the «dead» card reader so it just fired up the internal OS. No idea.
Boot to Desktop now takes around 10 seconds. With the HD it took around two Minutes until you were able to use ANYTHING. The Finder was there after 1 Minute or so, but you couldn't do anything, because it was beach balling forever.
It worked! The only thing i changed was the USB Port. It was plugged into the last port and i changed it to the first. Before, a card reader was plugged into the first port, but without a card inserted. Now i don't know what really happens, but MAYBE the Mac checks each USB port in (1,2,3,4) order on startup, and it somehow took too long for a response of the «dead» card reader so it just fired up the internal OS. No idea.
Boot to Desktop now takes around 10 seconds. With the HD it took around two Minutes until you were able to use ANYTHING. The Finder was there after 1 Minute or so, but you couldn't do anything, because it was beach balling forever.
Yup, found that as well... nevertheless... it does not work. I even tried to create a bootable disk following these instructions, but the SSD does not show up as a start volume when i start the mac with option held down... this is really frustrating.
Then i've found something about a T2 Chip, that prevents the Mac from starting from an external Device, but my late 2013 does not have one (according to systeminformation).
Same thing. It starts the installation (or whatever it does in the Finder), i select the external SSD as place to install. Runs to the point where it automatically restarts the iMac (tried both: wait 30 seconds for restart or click the button to restart), restarts (without the chime) and just buggers off to just starts up from the internal HD anyway...
Everywhere else i've read the SSD must be formatted Mac OS Extended (journaled) and GUID.
In theory the installer of Catalina should Convert the T5 Samsung drive to the correct drive format of APFS / GUID.
What happens if one reformatted it as APFS / GUID and run the installer again ?
Starting in Mojave macOS 10.14.3 and above - the Official Apple Drive format requires APFS / GUID.
Ah - was going to alert to Catalina not liking an Bootable External Drive with additional Drives attached but you already discovered this.
Good Luck
Catalina Installation «fails» on external SSD
