How easy is it to run iMac off external drive?

[kramden88]

My 2019 iMac is terribly slow. In fact, it's been that way all along. Currently takes 15-20 minutes to complete a reboot. I suspect it's either the Fusion Drive or the logic board. I can't afford to buy a new machine at the moment and I'm not really up to the task of replacing the internal drive.

If I transfer everything to an external Thunderbolt drive, do I have to update the paths of things like my Photo library, CCC backups, Time Machine backups, etc.? I'm just trying to figure out how involved this will be before I buy anything.

 

[HobeSoundDarryl]

No, hold down the option key while booting up and choose the external drive as the boot drive.

This page gives rich detail. It will show you how to specify the external as the startup drive so it will be the one to boot the system. All of your photo library, music library, etc can be moved to the external to then seem exactly as they do now... except the boot will be very quick.

 

[ovbacon]

My 2019 iMac is terribly slow. In fact, it's been that way all along. Currently takes 15-20 minutes to complete a reboot. I suspect it's either the Fusion Drive or the logic board. I can't afford to buy a new machine at the moment and I'm not really up to the task of replacing the internal drive.

If I transfer everything to an external Thunderbolt drive, do I have to update the paths of things like my Photo library, CCC backups, Time Machine backups, etc.? I'm just trying to figure out how involved this will be before I buy anything.

I have a 2015 iMac 5K that had (has) a failing fusion drive. I now run the imac from a external 2TB ssd. How etc can be found at the end of this macrumors thread. It doesn't boot fast but once running it is stable and pretty decent.

 

[ovbacon]

Also download DriveDX (you can run it in test/free mode) to test your mac because this tool showed me that my problem was a near death ssd of the fusion drive.

 

[Fishrrman]

A 2019 iMac has USBc (which is USB3.1 gen2).
It's still got plenty of life in it.

You can get read speeds of about 900MBps when using an external USB3.1 gen2 SSD.

So my suggestion is that you get one of these:

SAMSUNG T7 Shield 1TB, up to 1050MB/s, USB 3.2 Gen2, Rugged, IP65 Rated, for Photographers, Content Creators and Gaming, Portable External Solid State Drive (MU-PE1T0S/AM, 2022), Black

Samsung T7 Shield Portable SSD delivers high performance on-the-go, not matter the terrain. It has an IP65 rating for water1 and dust2 resistance, with Dynamic Thermal Guard to manage heat control. Transfer huge files instantly. USB 3.2 Gen 2 and PCIe® NVMe achieve soaring sequential read/write ...

www.amazon.com

Format it to APFS, GUID partition format.

Then download SuperDuper from here:
download <click this link

SuperDuper is remarkably easy to use, and it's FREE to use for what we're going to do.

Use SD to clone your internal drive to the SSD.
(note, you didn't tell us how large the fusion drive is, or how much of it was currently "used").

When done, go to the startup disk preference pane, and set the SSD to be the new boot drive.

Reboot.
Do you get a "good boot" from the SSD?
Congratulations, you're done.

You'll come back here and post (to wit), "I never would have believed something so simple could make such a difference!"