Wouldn't that be Terraform (perfect for setting up cloud infrastructure) vs. Ansible (can do all, but more geared to provisioning servers you already have)?

Ansible uses Apache Libcloud to run just about anything you need on any cloud provider in terms of provisioning. Once provisioned, it will handle all of your various configuration and deployment on those.

Also plays really nicely with Terraform.

How does ansible make it straighftorward? As far as I know, it neither helps with networking failover, load balancing, data consistency, or other aspects of distributed systems, and running one application across clouds is certainly a distributed systems problem, not a deployment problem.

Ansible helps deploy software, but deploying software is the smallest problem of going multi-cloud.

See reply to other comment.

I know what ansible is and can do. Your other comment is about how it can provision and deploy things. While true, it's unrelated to my point that that's the least of your problems in a multi-cloud world.

A lot of that depends on scale too. I was mostly talking about the ability to standardize configuration so that you could replicate your infrastructure on multiple providers. Essentially just making sure that you have a backup plan/redundancy in case something happens and you find yourself needing to spin things up elsewhere on short notice.

You're absolutely right that running them at the same time, data syncing, traffic flow, etc is much more complicated.

Also check out Mist.io. It's an open source multi-cloud management platform that abstracts the infrastructure layer to help you avoid the lock-in.

Disclosure: I'm one of the founders.

What's the difference between mist.io and Apache's libcloud?

Ansible is great a doing the things that Ansible does!