etcd

全てのクラスタのデータを保存ふる一貫性と高可用性を持つキーバリューストア

Consistent and highly-available key value store used as Kubernetes' backing store for all cluster data.

If your Kubernetes cluster uses etcd as its backing store, make sure you have a back up plan for the data.

You can find in-depth information about etcd in the official documentation.