[linux-lvm] changing pe size

[linux-lvm] changing pe size

[Joe Pruett]

 i have looked around the net and not found much info about this...

i have a centos 5 system with a 32m pe size vg and have attached some
storage with an lvm1 4m pe size vg.  i converted the old vg to lvm2
without problem, but i would like to merge the volumes and pvmove data
onto the newer 32m pe pvs.  but you can't merge things with different pe
size, so i've been trying to get the 4m pe vg changed to 32m pe.  after
much monkeying around i was able to get all the pvs and lvs to have le
counts that were the right size to be convertible to 32m pe.  but it
looks like each segment must be sized appropriately and i can't find a
way to merge segments together so that things are sized correctly.

the most recent error is:
# vgchange -s 32m lv
  New size 209051648 for disk0 segment length not an exact number of new
extents.

would i be better off converting the 32m pe vg to 4m pe?  this is all
with lvm2 now, and what i read says that the 64k segment limit doesn't
exist anymore, so 4m pe isn't a limiting factor for lv sizing.  or is
there a way i can combine segments so they are sized appropriately? 
i've got enough space that i should be able to pvmove stuff around to
coalesce segments, but it isn't clear if there is a tool to do that.

if all else fails, i guess i'll just have to do a filesystem level copy
onto the 32m pe vg.  or is there some other magic i'm missing?

Re: [linux-lvm] changing pe size

[Joe Pruett]

> i have looked around the net and not found much info about this...

so i spent time experimenting...

> i have a centos 5 system with a 32m pe size vg and have attached some
> storage with an lvm1 4m pe size vg.  i converted the old vg to lvm2
> without problem, but i would like to merge the volumes and pvmove data
> onto the newer 32m pe pvs.  but you can't merge things with different pe
> size, so i've been trying to get the 4m pe vg changed to 32m pe.  after
> much monkeying around i was able to get all the pvs and lvs to have le
> counts that were the right size to be convertible to 32m pe.  but it
> looks like each segment must be sized appropriately and i can't find a
> way to merge segments together so that things are sized correctly.

it turns out that pvmove will coalesce adjecent segments.  so i was able 
to use a series of pvmoves to get all my segments to be contiguous and a 
mulitple of the new pe size i wanted.

once i did that, then vgchange -s worked just fine.