>What's wrong with setting up kvm "gold" images for your various server types (db server, redis instance, ha proxy server etc.) and then just dd'ing those image

>What's wrong with setting up kvm "gold" images for your various server types (db server, redis instance, ha proxy server etc.) and then just dd'ing those images to host machines and using ansible/puppet/chef to do any final role configuration on first boot? You're leaving out the other attractive aspects of Docker/containers: performance, lower cpu utilization, instant spin up, less disk space, etc. Those factors lead to higher density of images on servers. Puppet/Chef + hypervisors can't compete with those particular factors. In summary: Containers have less isolation, but can be more densely packed. VMs have more isolation, but less densely packed. The 2 technologies have different tradeoffs and economics.