Slow boot from external SSD on new 27" iMac 2019

[larzy]

Can anyone explain why the Samsung T5 ssd connected via USB-C to a new 27" iMac 2019 boots slowly? I read somewhere in this forum that in Catalina, because of APFS, the boot sequence search for devices, so there's a delay when the Apple logo comes on. And it's not just a few seconds - it's slower then the fusion drive.

I tried deleting the original 2TB Fusion drive that came with a Mac OS when I received the machine, but the booting proces still takes longer then it should.

Today I tried buying an Samsung X5 500gb ssd that connects via TB3 cables - and that seems to be a bit quicker. So that could be a solution.

But my question is, is it impossible at this time, to find a solution to my setup so I can use my 2TB Samsung T5 drive as a boot and main drive? I had hoped it was possible and was quite surprise to see and learn that there is some sort of hick-up. I don't wanna carboncopy anything - I just want a clean install and want to run the operation system from an external ssd.

 

[CheesePuff]

Hmm, I use the T5 as my boot drive on my 2015 iMac 27" and there is almost no delay from power to the Apple logo/progress bar starting.

 

[CoastalOR]

OP: Can you confirm that the 2TB Samsung T5 drive is set as the Startup Disk in the System Preferences?

 

[larzy]

OP: Can you confirm that the 2TB Samsung T5 drive is set as the Startup Disk in the System Preferences?

Yes I changed that to be the default boot drive.

As far as I can read the problem is in Catalina (and Mojave) since they require to run on APFS filesystem where Apple changes some things for external booting.

That’s what I have found out - which is very bad and problematic if that’s the case.

Because all you hear is if you want to improve an old or new iMac with a spinning hard drive or fusion drive with both, the way to do is buy and external ssd and boot the operation system from there.

The true TB3 drive I purchased yesterday almost has no lag and is faster. I just wished I didn’t have to spend the money since I already have the Samsung T5 2TB ssd that I planned on using. But that is USB-C 3.1 and apparently even though it’s fast, it’s halted by the APFS and Catalina boot process.