[wmertens]

* NixOps lets you define the complete layout of your deployment (in Nix, obviously): how many VMs, what they should be running, where they should be running.

* NixOps works on whole machine + transformation of machine level: NixOps builds all system configurations of the whole network, then makes sure the required target hosts are available, then copies the builds to the hosts, and then atomically switches all hosts to the new configuration at once. NixOS is stateless, and a new config only means that the new service configurations are applied.

Rollback is a matter of switching all VMs back to their previous configurations, takes less than a minute in all.

[jacques_chester]

Thankyou for the additional detail. I'd say that the two arrived at similar outcomes, which isn't surprising given NixOps's roots.