lvcreate is demanding 4 PE/ 16 MiB extra

[say-paul]

I am trying to build an raw image using Image builder where I specify the LV's , the PV is computed correctly with a 1 MiB padding for metadata, but lvcreate complaining 4 PE short, adding that in the PV I get no error, but cannot find any logical reason for the extra space demanded by lvcreate.

the PR I am working on for error details

[zkabelac]

Not sure where is the problem on lvm2 side here.
pvcreate by design currently aligns metadata area on 1MiB.
vgcreate by default uses 4MiB extent size - so the LV can by allocated in 4MiB steps/units.
All of these settings are fully configurable by options - and user can select values in range of 512B to 4GiB in range.

The only 'limiting' factor can be the 'maximal' volume size size the size is expressed as num_of_extents (32bit) * extent_size(32bit) -> final_size (64bit)

So 4MiB extent size limits users to maximal VG size of 16PiB.
4KiB extent size -> 16TiB.

Final note - drives often come with various internal alignment rules - i.e. 512KiB is typical SSD/NVMe allocation unit so it's good idea to keep things aligned here as well.

So i.e. if you know max VG size will be 1TiB - you can use 'vgcreate -s 4k /dev/xxxx' and you can likely use all the PV space. Though if you will 1MiB alignment on PV header you can probably stay at 1MiB extent size as well.