I have no objection to extended and logical partitions on pure MBR drives, but on disks with hybrid MBRs
, as under discussion in this thread, use of extended and logical partitions is outright foolhardy. To the best of my knowledge, no utility supports creating such a monstrosity. The core of the reason why is that logical partitions require data structures (known as Extended Boot Records, or EBRs
) that exist just before the partitions they define. GPT has no such requirements; all GPT partitions are defined entirely within the main GPT data structures at the start and end of the disk. This will limit which GPT partitions you can turn into hybrid logical partitions. Worse, suppose you create a hybrid table with a logical partition that's legal because there's a gap between two partitions, so the EBR can reside in that gap. Now suppose you decide you want to create a new GPT partition between those two partitions. The new GPT partition now occupies space legally in the GPT, but it overlaps that critical EBR. This might work for a while, but as soon as you write data (legally from a GPT perspective) to the sector with the EBR, you'll scramble the definition of that logical partition and you'll lose all access to any subsequent logical partitions (because logical partitions are defined using what's known as a linked-list data structure, in which one entry contains a pointer to the next, so if one is damaged you lose all the rest).
There are a host of similar problems with implementing a hybrid MBR that utilizes extended/logical partitions. Although it would be possible for any one program to disentangle some or all of the messes that could ensue from this sort of system, there's no way to guarantee that other programs would do the same. That is, suppose somebody wrote RecklessGPT, the GPT partitioning tool that lets you create a hybrid MBR with extended and logical partitions. RecklessGPT might prevent you from creating a GPT partition that occupies the space needed by the EBR; however, the user might just use GParted, GPT fdisk, OS X's Disk Utility, or some other tool to edit the partition table, and those programs do not provide such protections, so you could easily get into trouble.
So to sum up, I will not "bring it down a notch." I understand you did not realize how dangerous what you were suggesting was, but I do. I've given the matter a fair amount of thought. I've seen the problems that even run-of-the-mill hybrid MBRs cause, and the thought of hybrid MBRs with extended and logical partitions gives me the screaming heebie-jeebies.