Comment 15 for bug 1334974

This is interesting because if you select an image to create a new volume to boot from, it works
in my case, Micro-Small has a 50GB root disk, the image used is 2.1GB qcow2

e.g.
nova boot --poll --flavor Micro-Small --block-device source=image,id=da3c219e-591d-4939-b930-15807b8d0e48,dest=volume,size=70,shutdown=preserve,bootindex=0 alop-boot-from-vol-cli-larger
Server building... 100% complete
Finished

However, if I were to have created a cinder volume first
cinder create --image-id da3c219e-591d-4939-b930-15807b8d0e48 --display-name vol-boot-test-cli2 55
nova boot --poll --boot-volume 11a02844-59a5-46dc-a78f-e4a1dbb5bf3f --flavor Micro-Small --block-device id=11a02844-59a5-46dc-a78f-e4a1dbb5bf3f,source=volume,shutdown=preserve alop-boot-from-vol-cli-larger
ERROR: Flavor's disk is too small for requested image. (HTTP 400) (Request-ID: req-4ca9fb7a-0632-403e-bc22-0a5a682ae1e2)