Dne 9.3.2017 v 12:12 Eric Ren napsal(a):
Hello,

I find that it will fail to create a thin pool with all the free PE in VG as
follows:

# pvs
  PV         VG   Fmt  Attr PSize   PFree
  /dev/sdb        lvm2 ---  200.00g 200.00g
# vgcreate vgtest /dev/sdb
  Volume group "vgtest" successfully created
# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sdb
  VG Name               vgtest
  PV Size               200.00 GiB / not usable 32.00 MiB
  Allocatable           yes
  PE Size               4.00 MiB
  Total PE              51192
  Free PE               51192
  Allocated PE          0
  PV UUID               JD74c2-R4zZ-cgs5-c5Ty-1abQ-cf7l-gdSxzz
# lvcreate -l 51192 --thinpool thinpool0 vgtest
  Volume group "vgtest" has insufficient free space (51167 extents): 51192
required.

while it works when specifying '-l' this way:

# lvcreate -l 100%FREE --thinpool thinpool0 vgtest
  Logical volume "thinpool0" created.

Is this something by design? or something may be wrong?
I can replicate this on both:

Hi

Yes this is by DESIGN

When you specify '-l|-L'  you specify size of 'dataLV'  (logical size)
But then you need some more space for 'metadata' LVs (_tmeta & _pmspare)

-l100%FREE figure this automagically and reduces size a bit to fit in metadata 
LV.


Some 'future' version of lvm2 may support something like '--physicalsize' which will be 'a total size used for every allocation made by command).


Regards

Zdenek

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