A technique maintains multiple copies of data served by storage nodes of a cluster during upgrade of a storage node to ensure continuous protection of the data served by the nodes. The data is logically organized as one or more volumes on storage devices of the cluster and includes metadata that describe the data of each volume. A data protection system may be configured to maintain two copies of the data in the cluster during upgrade to a storage node that is assigned to host one of the copies of the data but that is taken offline during the upgrade. As a result, a slice service of the node may become unavailable during the upgrade. In response to the unavailability of the slice service, the technique redirects replicated data targeted to the slice service to a standby slice service according to a degraded redundant metadata (DRuM) service of the cluster.