At least in the case of KVM, it's a very heavy-weight solution. Hardware virtualisation takes more RAM, and the I/O is substantially lower. I think hardware vir

At least in the case of KVM, it's a very heavy-weight solution. Hardware virtualisation takes more RAM, and the I/O is substantially lower. I think hardware virtualisation (e.g. KVM) should only be used when the use-case demands it (e.g. Windows, OS development, or legacy applications). As for why Docker? Dunno. While I think illumos zones are pretty awesome myself, having a standardised format is handy. Docker is also popularising the container mantra with Linux.