Comment 13 for bug 1190559

Nova fails to boot an instance when virtual_size of the image is larger than flavor(disk size) used to boot the instance. As virtual size (only size is checked) is not checked by nova scheduler to schedule instance any of the compute node. Once instance is scheduled then hypervisor of the scheduled compute node checks the virtual size of the image and if the virtual size is larger then the disk allocated, it fails to boot instance.
So, if virtual size matches the image size, then nova will not fail to boot instance because of such reasons. I also feel that this should be changed to high importance.