I see how that was confusing. I meant that the fact that Swarm doesn't offer such a guarantee is the reason that storing the data on the host isn't a solution. My real complaint is that none of these give you a way to do persistence that doesn't destroy some other really nice properties of containers. There's lots of people trying to fix this problem the right way, Kubernetes has made a lot of progress on having volumes follow the containers around from host to host. Torus is a slightly different approach, Flocker is another one.

> I don't think it's docker's responsibility to solve database clustering.

I don't know if I'd call it a responsibility. But Docker is obviously trying to expand their platform into more and more aspects of containerization. If they figured out persistence that would really set them apart, something that this product doesn't really do. It mostly just keeps them even with Kubernetes at best. And an imitation of it at worst.