On Mon, 9 Nov 2009, Doug Ledford wrote:

Of course, I recently had a bug report that I ended closing out as 
NOTABUG because of this very ability.  The person had arrays with 1.2 
superblocks, and they went to add a new disk, and all the existing disks 
had a specific partition layout, so he copied that to the new disk, then 
tried to add the partition to the raid array.  It kept returning "device 
too small for array".  Then, upon inspection, we come to see he has a 
1.2 superblock on the *entire* drive, which left the partition table 
intact, but the partition table is *pointless* because the array is on 
the whole disk devices.  This sort of confusion is bad.  So, while I 
could see making it 1.2 for partitions (so that boot sectors won't 
overwrite the superblock), I wouldn't make it 1.2 for whole disk 
devices, and in fact it might be wise to refuse to create 1.2 
superblocks on whole disk devices.  Just a thought.

Well, same thing there, if you create a partition table you don't break 
the superblock. Perhaps something needs to be able to discern between the 
superblock being "whole disk" and on a partition? Personally I put 1.2 on 
"whole disk" (no partition table at all), and I would really HATE this 
possibility going away. I like it the way it is and feel comfortable with 
it and I don't want 1.0 or 1.1 superblocks in my setup.

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se