It's not recommended to remove the taints and tolerations settings.

The affinity settings ensure pods are scheduled to the correct node pool. It's recommended not to remove these settings.

https://cloud.google.com/storage/pricing#cloud-storage-always-free may have the answer.

The next thing to check would be the backup job logs with this command. If the backup succeeded, there should be 1 or more volumesnapshot objects created. kubectl logs -n apigee

kubectl get pv will show the storage class used by the Cassandra volumes.