External Booting on 2014 Mac Mini

[mactectom]

For a while now, when attempting to boot from an external drive, my 2014 Mac mini keeps booting from the internal drive. Iv discovered that if I unplug the other USB drives from the Mac (time machine and media drive), it will boot from the external ssd. But, I have to do that every time I start up my machine. I think this started with the Mojave update, but not sure. Any fix for this?

 

[Fishrrman]

Don't want to insult you, but have you tried:

Booting with the option key held down continuously until the startup manager appears?
and then...
...Going to the startup disk preference pane and designating the external drive to be the boot drive?

By the way...
Are all the external drives "bus powered"? (i.e., not using their own power supplies).
With several drives connected, perhaps the USB bus power isn't enough to get that boot SSD "up and running" before the Mini "looks elsewhere" and "finds" the internal drive...

 

[keysofanxiety]

As Fishr said, hold Alt on startup to select all disks. Navigate to the boot drive you want to be default by using your arrow keys and then hold CTRL. The icon will change (making it the default boot drive) and then press Enter to boot into it.

Any better from there?

 

[inmnbob]

This works well for me. I have an external ssd as the boot drive.

 

[Boyd01]

I'm thinking along the same lines as Fishrrman, that the Mini isn't providing enough current for the SSD to be recognized at boot time. Maybe some change in the current draw for your disk(s), or some power issue on the Mini itself? There are some inexpensive USB testers that might help if you can't solve this another way

https://www.amazon.com/USB-Charger-Doctor-line-Voltage/dp/B00S80CMBO
https://www.amazon.com/PowerJive-Voltage-Multimeter-chargers-capacity/dp/B013FANC9W