import/export with --export-format 2

Hi, src-image is 1GB (provisioned size). I did the following 3 tests. 1. rbd export src-image - | rbd import - dst-image 2. rbd export --export-format 2 src-image - | rbd import --export-format 2 - dst-image 3. rbd export --export-format 2 src-image - | rbd import - dst-image With #1 and #2, dst-image size (rbd info) is the same as src-image, which is expected. With #3, dst-image size (rbd info) is close to used size (rbd du), not the provisioned size of src-image. I'm not sure if this image is actually useable when write into it. The questions is that, is #3 not supposed to be used at all? I checked doc, didn't see something like "--export-format 2 has to be used for importing the image which is exported with --export-format 2 option". Any comments? Thanks! Tony