ECK: Document recovery from failed volume upsize

troubleshoot/deployments/cloud-on-k8s/common-problems.md

@@ -306,3 +306,14 @@ Check that the role mapping was deleted:
 GET /_security/role_mapping/<roleName>
 {}
 ```
+
+
+## If a volume expansion failed [k8s-common-problems-volume-failed-expansion]
+
+If you attempted an expansion of an {{es}} volume via its [volume claim template](/deploy-manage/deploy/cloud-on-k8s/volume-claim-templates.md#k8s-volume-claim-templates-update), you may have encountered scenarios where the operation failed such as Azure not allowing volume expansion without shutting down the Virtual Machine to which it is attached. If you try to adjust the volume claim template back to the original size you will encounter a failure:
+
+```
+Failed to apply spec change: handle volume expansion: decreasing storage size is not supported: an attempt was made to decrease storage size for claim elasticsearch-data
+```
+
+In this scenario the best course of action is to rename the existing `nodeSet` to a new name while simultaneously updating the volume claim template to the original size. This operation will bring a new `StatefulSet` online while moving all existing indices to the new volumes, and will delete the old `StatefulSet` and its volumes once the operation is complete.