Nova - boot from volume - Min Disk Size - Liberty

[Ross Martyn]

Description
===========
Seemingly incorrect validation of image requirements for instance when using boot from volume functionality.

Steps to reproduce
==================
* Create an image with a minimum disk size (Eg 2GB)
* Create a bootable volume from image (Eg 2GB)
* Launch an flavor with 1GB RAM (root disk set to 40Gb in our case, but not expected to be used during boot from volume).

Expected result
===============
In this case the instance should be created, as the image minimum requirements are met.

Actual result
=============
Volume is smaller than the minimum size specified in image metadata. Volume size is 1073741824 bytes, minimum size is 2147483648 bytes

This is incorrect volume size is LARGER than nova api is reporting, we thought this may be reporting the RAM size, rather than the disk size, however we disproved this by doubling the minimum disk size, and using a 2GB RAM instance. This succeeded.

Stumpt! For now, we have removed minimum disk sizes.

Environment
===========
1. OpenStack Liberty on Ubuntu14.04 w/ Ceph Jewel.

dpkg -l |grep nova
ii nova-api 2:12.0.3-0ubuntu1~cloud0

2. Libvirt+KVM (Unrelated, fails/refused(400) during API Call.

3. CEPH backed volumes/images and ephemeral disks

4. Neutron in use, but i expect also unrelated.

Logs & Configs
==============
The main log is the following.

2016-10-13 10:21:01.471 24901 DEBUG nova.api.openstack.wsgi .... Returning 400 to user: Volume is smaller than the minimum size specified in image metadata. Volume size is 1073741824 bytes, minimum size is 2147
483648 bytes. __call__ /usr/lib/python2.7/dist-packages/nova/api/openstack/wsgi.py:1175

[Marc Gariépy (mgariepy)]

I'm also affected by this issue on Mitaka release..

[Sean Dague (sdague)]

Automatically discovered version liberty in description. If this is incorrect, please update the description to include 'nova version: ...'