etcd is sensitive to IO latencies and DRBD mode C (which ganeti uses to ensure disk consistency between primary and secondary) causes by definition this to increase. Not only that, but at times a full DRBD re-sync might be required from primary to secondary, inducing a period during which writes to etcd are going to be throttled. The Kubernetes cluster could suffer because of that. Since etcd is a replicated datastore with HA built-in there is really no reason to add the extra layer of complexity and latency DRBD adds. Switching all etcd VMs to the plain disk template would solve this issue. The drawback would be a bit more complicated ganeti cluster maintenance operations (knowing that etcd is plain and ignoring it during migrations)