Tested in Proxmox 3.2
Same result,
INFO: status: 15% (82566119424/536870912000), sparse 15% (82110078976), duration 27, 3736/14 MB/s
INFO: status: 16% (87087448064/536870912000), sparse 16% (85914935296), duration 37, 452/71 MB/s
INFO: status: 18% (99618586624/536870912000), sparse 18%...