<p>I have deployments on one Kubernetes cluster that I might want to move to another Kubernetes cluster in the future. Is it possible to combine these two clusters or must I redeploy everything? If the answer is yes, what if there are StatefulSets?</p>

Mike
<p>The short answer is no. </p>

<p>You can connect to clusters with something like <a href="https://kubernetes.io/docs/concepts/cluster-administration/federation/" rel="nofollow noreferrer">Kubernetes Federation</a> or if you have Calico, you can use something like <a href="https://docs.projectcalico.org/v3.2/usage/configuration/bgp" rel="nofollow noreferrer">BGP peering</a></p>

<p>You'll have to redeploy everything and in the case of StatefulSets, it really depends where you are storing your state. For example:</p>

<ul>
<li>Is it MySql? Backup your db and restore it in the new place.</li>
<li>Is it Cassandra? Can you reattach the same physical volumes in the cloud provider? if not, then you'll have to transfer your data.</li>
<li>Is it etcd, Consul or Zookeeper? Can you back it up or attach the same physical volumes?</li>
</ul>
