What do iotop and top look like on the system while the docker load or docker save commands are running?
This does seem to be a bit slow:
>>> (7*1024.)/30/60
3.982222222222222
>>> (10*1024.)/30/60
5.688888888888888
In 30 minutes, it averages reading the compressed data at about 4mb/sec, and writing the uncompressed data at 5.6mb/sec. Is your cpu pegged during this operation?