Description of problem:
Looks like when encrypted && clear volumes attached to an instance , both sharing the same lsblk disk size.
When extending the volume in use , the size of the encrypted volume bigger than the clear one ,
[Titan92 setup with a fix for permission issue]
Why ?

1. created two volumes empty , 1 clear size = 1G , 1 encrypted with luks size = 1G
   Created an instance and attached both the instance

From lsblk -lb

$ lsblk -lb
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vda 253:0 0 2147483648 0 disk
vda1 253:1 0 2138029568 0 part /
vda15 253:15 0 8388608 0 part
vdb 253:16 0 1073741824 0 disk
vdc 253:32 0 1073741824 0 disk

1. 1. 1. It looks like both disk sharing the same size

1. nova extend command for both:

cinder --os-volume-api-version 3.59 extend 537ae37f-ec46-4259-8215-048606c7f964 2
cinder --os-volume-api-version 3.59 extend 83c20fa9-244a-4875-9f28-b5e323d559c9 2

(overcloud) [stack@undercloud-0 tempest]$ cinder list
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1. checking lsblk size on instance:
   $ lsblk -nlb
   vda 253:0 0 2147483648 0 disk
   vda1 253:1 0 2138029568 0 part /
   vda15 253:15 0 8388608 0 part
   vdb 253:16 0 2147483648 0 disk
   vdc 253:32 0 2145415168 0 disk

When tested on netapp backend ,
attached encrypted volume size is not the same as clear volume .
RBD behaviour is different from others and probably will cause us issues related to migrating / copying and more ...