During the development and review process of the disk health indicator we noticed that it was hard to understand. Since we learnt a lot from the first round of development we want to go through the code one more time and restructure it.
server/src/test/java/org/elasticsearch/health/node/DiskHealthIndicatorServiceTests.java
public static final Set<DiscoveryNodeRole> DATA_ROLES = Set.of(
        DiscoveryNodeRole.DATA_ROLE,
        DiscoveryNodeRole.DATA_COLD_NODE_ROLE,
        DiscoveryNodeRole.DATA_FROZEN_NODE_ROLE,
        DiscoveryNodeRole.DATA_HOT_NODE_ROLE,
        DiscoveryNodeRole.DATA_CONTENT_NODE_ROLE,
        DiscoveryNodeRole.DATA_WARM_NODE_ROLE
    );
    public static final Set<DiscoveryNodeRole> NON_DATA_ROLES = Set.of(
        DiscoveryNodeRole.MASTER_ROLE,
        DiscoveryNodeRole.ML_ROLE,
        DiscoveryNodeRole.INGEST_ROLE,
        DiscoveryNodeRole.VOTING_ONLY_NODE_ROLE,
        DiscoveryNodeRole.REMOTE_CLUSTER_CLIENT_ROLE,
        DiscoveryNodeRole.TRANSFORM_ROLE
    );
    
    public static final Set<DiscoveryNodeRole> OTHER_ROLES = Set.of(
        DiscoveryNodeRole.ML_ROLE,
        DiscoveryNodeRole.INGEST_ROLE,
        DiscoveryNodeRole.VOTING_ONLY_NODE_ROLE,
        DiscoveryNodeRole.REMOTE_CLUSTER_CLIENT_ROLE,
        DiscoveryNodeRole.TRANSFORM_ROLE
    );