Ceph

rbd import foo bar output:
rbd import file_pos=0 extent_len=12288
reading 12288 bytes at offset 0
rbd import file_pos=1048576 extent_len=278528
reading 278528 bytes at offset 1048576
rbd import file_pos=1331200 extent_len=4096
reading 4096 bytes at offset 1331200

rbd export output:
writing 12288 bytes at ofs 0
writing 1335296 bytes at ofs 4194304
writing 4096 bytes at ofs 9437184

As you can see, the offsets don't match. They do not match for real, and this also affects other librbd clients, like qemu-img and qemu itself.