Comment 1 for bug 1163844

Started thread on the mailing list: http://lists.openstack.org/pipermail/openstack-dev/2013-April/007478.html

The behavior when the disk shrinks is inconsistent across all the hypervisors.

libvirt: logs it cannot resize to smaller and just keeps the larger disk
xen: tries to copy contents to a smaller disk, fails if too large
hyperv: always errors out if new disk size is smaller
powervm: silently keeps the larger disk
vmware: (couldn't find where migration code handled resize)

The only mention in the API guide - http://docs.openstack.org/api/openstack-compute/2/content/Resize_Server-d1e3707.html - is "scaling the server up or down."

Since Hyper-V always fails on a smaller disk and it can lead to being unable to access a VM, I would propose the behavior from libvirt and powervm be adopted and that this be addressed in the Nova v3 API and explicitly fail if we cannot resize down.