There are projects that help you run databases in kubernetes and also make backups of many things hosted:
- Automatic CephFS for your cluster -> https://rook.io/docs/rook/master/
- Backups for cluster resources and volumes -> https://github.com/heptio/ark
- Spin up dynamic postgres clusters -> https://github.com/zalando-incubator/postgres-operator
Databases are just applications with different resource needs. Please stop pushing forward the notion that they can't be run in containers or container orchestration systems. Databases are just programs. If the substrate for running your containers doensn't reliably support flock or fsync or something your database needs, then maybe pick a better substrate that does -- container runtimes these days and kubernetes don't stand in your way these days.
That's what I was doing until rook came around. If you're running in something like AWS (or even if you're not), you can also do something like attach an EBS volume (to a local host) and do that. Or, you can set up a plain ISCSI drive (or get one from your provider, even basic providers these days might offer storage that way) and use that.
There have been a LOT of choices for a long time.
https://twitter.com/kelseyhightower/status/96347131657256140...
He said "You still need to worry about database backups and restores. You need to consider downtime during cluster upgrades."
These things are totally true. K8s doesn't automate backups (edit: by default; though, it can) and if you need to take K8s down for upgrades, then everything is down. For its part, though, CockroachDB supports rolling upgrades with no downtime on Kubernetes.
As for routing, that is tough problem if you want to run K8s across multiple regions, though we have some folks who've done it.
And if one finds setting up StatefulSets challenging, we have a tutorial on how to do it written by a former Kubernetes engineer: https://www.cockroachlabs.com/docs/stable/orchestrate-cockro...