Moving external boot drive to a newer iMac

[techlectics1]

I have a late 2015 iMac. My 2TB fusion drive started failing so I purchased a 2TB external SSD and used migration assistant to move everything to the new external. This works very well except there are times when the os tries to access the internal HD and causes lengthy beach balls. Bootup can sometimes take 10 minutes or more, I assume because it's trying to access the defective internal for some reason. I have the option of buying a used 2019 iMac but it only has a 512GB internal SSD. Would I be able to seamlessly move my current external SSD to the 2019 iMac and boot from it as I am doing now?

 

[CoastalOR]

It should work if the external SSD has a macOS newer than 10.14.4 (10.14.5 or newer up to the latest macOS release). Apple does not support any older macOS than 10.14.4 for a 2019 iMac.

 

[Fishrrman]

"I have the option of buying a used 2019 iMac but it only has a 512GB internal SSD. Would I be able to seamlessly move my current external SSD to the 2019 iMac and boot from it as I am doing now?"

The internal SSD on the 2019 iMac will perform MUCH faster than booting/running from an external USB3 SSD.

If you get the new iMac, use the INTERNAL SSD for booting/running.

If "all your stuff" won't fit on the internal, than re-purpose the existing external SSD to become your "supplemental storage" drive.

 

[techlectics1]

Thanks all for the replies, very helpful.