I am trying to better understand disks, partitions, and partition tables (mbr vs gpt). In the process I checked the disks on one of my machines (single boot ubuntu 20.04), and found that all of my disks are gpt. However I also found out that some of the partitions have a partition table too. What got me even more confused is that the
/boot/efi partition is mbr even though it is on a disk that is gpt. At that point I wasn't sure whether the disk was gpt or otherwise so I tried to convert the
/boot/efi to gpt but in the process ended up rendering my machine unbootable. When I looked online for how to convert between the two styles I found that the conversion is done on the disk rather than the partition, but I already have my disk partitioned as gpt. So my question can be divided into three parts (and it all depends on my understanding as laid out above being correct):
1- What does it even mean to have a partition table inside a partition?
2- How can a disk be gpt but the
/boot/efi partition on it be mbr? And why?
3- If a system has two hard disks, but one operating system, can each one of these disks have their own different partition tables (one mbr the other gpt)?