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Comment by stcredzero | Hacker News Reader

Once you set it to boot from an external SSD, it will happily continue doing so.

What happens when the soldered-on SSD fails? Can you alter a setting in the PRAM or SMC to let the system completely disregard the failed SSD?

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Yes, if the soldered-on SSD has failed you can boot from an external drive by holding down the alt/option key while the system powers on to bring up the boot selection menu.

I thought this no longer works with the T2 chip? Don't you run into issues with e.g. upgrading the firmware because it will only accept firmware updates from the internal drive?

I got a brand new mac with a T2 chip this week from my work. The first thing I did was do all the updates, including a security update for the OS, which required a restart. During the restart it was giving errors, so it was not able to boot properly. It would just give the error message and you could only restart again, just to have the same thing happen. A colleague more familiar with macs, brought up a menu, where you could choose which drive to boot from, which eventually fixed the problem, since it booted from the hard disk. In my case this menu had only the internal ssd, since I did not have anything else connected. I would guess that if I had an external hard drive it would show up as well.

Also on the documentation of the T2 chip, Apple strongly recommends to use file vault, because if you do not, the ssd even though it is encrypted by default, gets decrypted [1] upon being mounted.

To sum up, I guess it is possible to boot from whatever device you want.

[1] https://support.apple.com/en-us/HT208344

It remembers which drive it boots from so as long as you keep the external drive connected it should boot from it

Still, another dongle to carry (with Mac Mini it's not that important) and a loss of speed/added latency for e.g. video editing. With normal usage patterns even USB 3.0 external thumb/SSD drives were just fine.

So use a tb3 enclosure with an nvme inside.

There are no bus-powered TB3 M.2 PCIe enclosures, and there never will be any[1]. This means you will have to buy a huge bulky externally-powered TB3 PCIe dock costing hundreds of dollars to accomplish this.

1. https://twitter.com/sephr/status/817883011165233152?s=19

No, it says there won’t be any that are sold unbundled.

"Still, another dongle to carry (with Mac Mini it's not that important) and a loss of speed/added latency for e.g. video editing. With normal usage patterns even USB 3.0 external thumb/SSD drives were just fine."

What is the speed difference between the on-board PCIe connected SSD vs. the USB3 connected SSD ? Aren't both PCIe and USB3 faster than the SSD, making it the bottleneck ?

A flash drive would, of course, be terribly slow ... do they make USB "thumb drives" that are SSD (not flash) ?

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