@brico said in Two HDD - 3 OS Win 10 - Multiboot:

Then we’ll restore on the first disk ! And destroy /dev/sda !

YES! You really need to be careful when deploying. While single partitions are even more tricky you have to be alert when deploying anyhow. Deploy will overwrite whatever is on disk. Thinks can go wrong if you don’t take care of what exactly you do.

So, we’ll try to create 2 hosts (for the same PC)

As you have seen, this is not possible. The basic concepts of FOG don’t allow for more than one host object in the database with the same MAC address.