As for migration, you might be able to create a degraded pool initially, copy over the data, and add the parity disk last.
I actually asked in the TrueNAS forum about this idea. According to some knowledgeable users this might work. For anyone interested, details here. The next major release (planned for end of October), should make this easier.
Thanks for saying this.
With recent campaigns and rants against digital media, people often claim that “you own the game if you buy a physical copy”. That always makes me sigh, because it’s false.
Not saying there are some advantages for some use cases, but I dislike hyperbole and untruths.