Re: Reg LVM PE Size and any limitations out of it

On Thu, May 29, 2025 at 10:36:07PM +0530, Lakshmi Narasimhan Sundararajan wrote:
> 2) Is there any limit to the max number of PE in a VG?
> It is not called out in any man pages, but an internet search gave me
> a max of 16M extents in a VG. So here I am asking for clarification,
> and worried if there is such a limit, would it limit then the VG
> capacity expansion to only 16M * 4M ~ 64 T [It did not though, I
> experimentally validated it].
> 3) under what scenarios does one need to consider applying
> physicalextentsize explicitly?
> I am trying to understand the usecase this came about.

I think I see where this is coming from. The top result on Google (at
least for me, but I imagine from your post it's similar for others), is
this 11 year old SuperUser question thread:

  https://superuser.com/questions/735600/size-of-extent-on-lvm2

The poster incorrectly links to an old HP manual describing the limits
for the *HP-UX* Logical Volume Manager:

  https://docstore.mik.ua/manuals/hp-ux/en/5992-4589/apa.html

Although Linux LVM1 (long since ancient history) was inspired by the
HP-UX tools the tables at this URL have nothing to do with Linux LVM,
especially lvm2.

I agree this belongs in a man page, and shouldn't take so much searching
to track down.

Regards,
Bryn.