EFI System Partitions: a hidden problem?

A lot of the more in-depth stuff around macOS isn't publicly documented by Apple, and Howard Oakley often tries to find out and blog about it on eclecticlight.co.

For instance, I've been experimenting with APFS fusion drives. This is basically the macOS equivalent of a RAID0 volume except there's some added intelligence on stuff that can be cached on the fastest drive.

So for fun, on my Mac Mini, I plugged in an external drive and tried to create a fusion drive across the internal and external drive. Nothing is documented about this process, do you have to google and piece together the procedure.

Of course it seems to work and then the volume corrupts itself. But why? This other guy who blogged about this, doesn't know.

Linux is much better about this. People do crazy shenanigans with their hardware all the time. You want to RAID-5 a bunch of USB sticks? Sure, no problem :)