[linux-lvm] Usable space in PV

Zdenek Kabelac zkabelac at redhat.com
Thu Oct 1 11:26:15 UTC 2015

Dne 30.9.2015 v 17:28 Timofey Koolin napsal(a):
> Task: calc usable space of PV before create PV and before create partition for
> PV.
> In my experiments usable space in PV = PVSize / ExtentSize * ExtentSize with
> integer operations.
> But when Metadata may be large - when LVM have a lot of logical volumes and it
> can take more space.
> I found in /etc/lvm/lvm.conf parameter pvmetadatasize = 255 secotors (default).
> What will if metadata will grow to more then 255 sectors?

If you plan to host lots of LVs within a single VG (in range of hundreds)
use i.e. 'pvcreate --metadatasize 5M'
(i.e. ~7000 linear single segment LVs  takes around 2.2MB and you need space 
for at least 2 metadatas to fit in)

What I'm not quite sure is your 'task' - what's the purpose ?
Do you want to do some 'sector' precise emulation of what lvm2 is doing by 
watching resuls of couple command with just subset of it's options ?

Isn't better to read man pages ?


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