diff --git a/server/src/main/java/org/elasticsearch/cluster/node/DiscoveryNodes.java b/server/src/main/java/org/elasticsearch/cluster/node/DiscoveryNodes.java
index 12c698a6ed958..5e6dec7b68062 100644
--- a/server/src/main/java/org/elasticsearch/cluster/node/DiscoveryNodes.java
+++ b/server/src/main/java/org/elasticsearch/cluster/node/DiscoveryNodes.java
@@ -65,7 +65,6 @@ public class DiscoveryNodes implements Iterable<DiscoveryNode>, SimpleDiffable<D
     private final String localNodeId;
     @Nullable
     private final DiscoveryNode localNode;
-    private final Version minNonClientNodeVersion;
     private final Version maxNodeVersion;
     private final Version minNodeVersion;
     private final IndexVersion maxDataNodeCompatibleIndexVersion;
@@ -81,7 +80,6 @@ private DiscoveryNodes(
         Map<String, DiscoveryNode> ingestNodes,
         @Nullable String masterNodeId,
         @Nullable String localNodeId,
-        Version minNonClientNodeVersion,
         Version maxNodeVersion,
         Version minNodeVersion,
         IndexVersion maxDataNodeCompatibleIndexVersion,
@@ -98,7 +96,6 @@ private DiscoveryNodes(
         assert (masterNodeId == null) == (masterNode == null);
         this.localNodeId = localNodeId;
         this.localNode = localNodeId == null ? null : nodes.get(localNodeId);
-        this.minNonClientNodeVersion = minNonClientNodeVersion;
         this.minNodeVersion = minNodeVersion;
         this.maxNodeVersion = maxNodeVersion;
         this.maxDataNodeCompatibleIndexVersion = maxDataNodeCompatibleIndexVersion;
@@ -117,7 +114,6 @@ public DiscoveryNodes withMasterNodeId(@Nullable String masterNodeId) {
             ingestNodes,
             masterNodeId,
             localNodeId,
-            minNonClientNodeVersion,
             maxNodeVersion,
             minNodeVersion,
             maxDataNodeCompatibleIndexVersion,
@@ -346,17 +342,6 @@ public boolean isMixedVersionCluster() {
         return minNodeVersion.equals(maxNodeVersion) == false;
     }
 
-    /**
-     * Returns the version of the node with the oldest version in the cluster that is not a client node
-     *
-     * If there are no non-client nodes, Version.CURRENT will be returned.
-     *
-     * @return the oldest version in the cluster
-     */
-    public Version getSmallestNonClientNodeVersion() {
-        return minNonClientNodeVersion;
-    }
-
     /**
      * Returns the highest index version supported by all data nodes in the cluster
      */
@@ -853,14 +838,12 @@ public DiscoveryNodes build() {
              */
             Version minNodeVersion = null;
             Version maxNodeVersion = null;
-            Version minNonClientNodeVersion = null;
             IndexVersion maxDataNodeCompatibleIndexVersion = null;
             IndexVersion minSupportedIndexVersion = null;
             for (Map.Entry<String, DiscoveryNode> nodeEntry : nodes.entrySet()) {
                 DiscoveryNode discoNode = nodeEntry.getValue();
                 Version version = discoNode.getVersion();
                 if (discoNode.canContainData() || discoNode.isMasterNode()) {
-                    minNonClientNodeVersion = min(minNonClientNodeVersion, version);
                     maxDataNodeCompatibleIndexVersion = min(maxDataNodeCompatibleIndexVersion, discoNode.getMaxIndexVersion());
                 }
                 minNodeVersion = min(minNodeVersion, version);
@@ -894,7 +877,6 @@ public DiscoveryNodes build() {
                 filteredNodes(nodes, DiscoveryNode::isIngestNode),
                 masterNodeId,
                 localNodeId,
-                Objects.requireNonNullElse(minNonClientNodeVersion, Version.CURRENT),
                 Objects.requireNonNullElse(maxNodeVersion, Version.CURRENT),
                 Objects.requireNonNullElse(minNodeVersion, Version.CURRENT.minimumCompatibilityVersion()),
                 Objects.requireNonNullElse(maxDataNodeCompatibleIndexVersion, IndexVersion.current()),
diff --git a/server/src/main/java/org/elasticsearch/indices/SystemIndexMappingUpdateService.java b/server/src/main/java/org/elasticsearch/indices/SystemIndexMappingUpdateService.java
index f65ed270e29c4..a00e8cdc138f6 100644
--- a/server/src/main/java/org/elasticsearch/indices/SystemIndexMappingUpdateService.java
+++ b/server/src/main/java/org/elasticsearch/indices/SystemIndexMappingUpdateService.java
@@ -93,7 +93,7 @@ public void clusterChanged(ClusterChangedEvent event) {
         }
 
         // if we're in a mixed-version cluster, exit
-        if (state.nodes().getMaxNodeVersion().after(state.nodes().getSmallestNonClientNodeVersion())) {
+        if (state.nodes().isMixedVersionCluster()) {
             logger.debug("Skipping system indices up-to-date check as cluster has mixed versions");
             return;
         }
diff --git a/server/src/test/java/org/elasticsearch/cluster/node/DiscoveryNodesTests.java b/server/src/test/java/org/elasticsearch/cluster/node/DiscoveryNodesTests.java
index 3264cf168b638..5101064f293e4 100644
--- a/server/src/test/java/org/elasticsearch/cluster/node/DiscoveryNodesTests.java
+++ b/server/src/test/java/org/elasticsearch/cluster/node/DiscoveryNodesTests.java
@@ -435,7 +435,6 @@ public void testMinMaxNodeVersions() {
 
         assertEquals(Version.fromString("5.0.17"), build.getMaxNodeVersion());
         assertEquals(Version.fromString("1.6.0"), build.getMinNodeVersion());
-        assertEquals(Version.fromString("2.1.0"), build.getSmallestNonClientNodeVersion());  // doesn't include 1.6.0 observer
         assertEquals(IndexVersion.fromId(2010099), build.getMaxDataNodeCompatibleIndexVersion());   // doesn't include 2000199 observer
         assertEquals(IndexVersion.fromId(2000099), build.getMinSupportedIndexVersion());            // also includes observers
     }
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/license/TransportPostStartTrialAction.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/license/TransportPostStartTrialAction.java
index 8a7ead2caf3be..212e593c9db98 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/license/TransportPostStartTrialAction.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/license/TransportPostStartTrialAction.java
@@ -55,7 +55,7 @@ protected void masterOperation(
         ClusterState state,
         ActionListener<PostStartTrialResponse> listener
     ) throws Exception {
-        if (state.nodes().getMaxNodeVersion().after(state.nodes().getSmallestNonClientNodeVersion())) {
+        if (state.nodes().isMixedVersionCluster()) {
             throw new IllegalStateException(
                 "Please ensure all nodes are on the same version before starting your trial, the highest node version in this cluster is ["
                     + state.nodes().getMaxNodeVersion()