Cinder doesn't check LVM extents count and extent size

[Ivan Kolodyazhny]

Checked extents on cmp after the test:
root@cmp:~# vgs -o +vg_free_count,vg_extent_count,vg_extent_size
  VG #PV #LV #SN Attr VSize VFree Free #Ext Ext
  cinder-volumes 1 0 0 wz--n- 20.00g 20.00g 5119 5119 4.00m
5119 extents * 4MB / 1024= 19,99609375 GB
when 20GB is 5120 LVM extents each by 4MB
It seems therefore cinder-volume gets the error from lvcreate command "Volume group "cinder-volumes" has insufficient free space (255 extents): 256 required."
Because 256 extents by 4MB is 1GB (size of the volume which we tried to create)

cinder-volume logs: http://paste.openstack.org/show/722748/

[Eric Harney (eharney)]

I'm not sure what you're suggesting -- but I don't think we should get into parsing extent usage etc. in LVM.

This may be a boundary case that just happens with small LVM deployments since we don't account for LVM overhead.

Does this happen with thin LVM or just thick?

[Ivan Kolodyazhny (e0ne)]

It was reproduced with thick provisioning.

"This may be a boundary case that just happens with small LVM deployments since we don't account for LVM overhead." - it's exactly what I have:(