diff --git a/src/main/java/org/apache/lucene/store/bytebuffer/ByteBufferDirectory.java b/src/main/java/org/apache/lucene/store/bytebuffer/ByteBufferDirectory.java
index c6c7ea922b3..7c4ef6dc41c 100644
--- a/src/main/java/org/apache/lucene/store/bytebuffer/ByteBufferDirectory.java
+++ b/src/main/java/org/apache/lucene/store/bytebuffer/ByteBufferDirectory.java
@@ -17,6 +17,7 @@ package org.apache.lucene.store.bytebuffer;
  * limitations under the License.
  */
 
+import com.google.common.collect.ImmutableSet;
 import org.apache.lucene.store.*;
 
 import java.io.FileNotFoundException;
@@ -48,6 +49,7 @@ public class ByteBufferDirectory extends Directory {
 
     final AtomicLong sizeInBytes = new AtomicLong();
 
+
     /**
      * Constructs a new directory using {@link PlainByteBufferAllocator}.
      */
@@ -112,10 +114,28 @@ public class ByteBufferDirectory extends Directory {
         return file.getLength();
     }
 
+    private final static ImmutableSet<String> SMALL_FILES_SUFFIXES = ImmutableSet.of(
+            "del", // 1 bit per doc
+            "cfe", // compound file metadata
+            "si", // segment info
+            "fnm"  // field info (metadata like omit norms etc)
+    );
+
+    private static boolean isSmallFile(String fileName) {
+        if (fileName.startsWith("segments")) {
+            return true;
+        }
+        if (fileName.lastIndexOf('.') > 0) {
+            String suffix = fileName.substring(fileName.lastIndexOf('.') + 1);
+            return SMALL_FILES_SUFFIXES.contains(suffix);
+        }
+        return false;
+    }
+
     @Override
     public IndexOutput createOutput(String name, IOContext context) throws IOException {
         ByteBufferAllocator.Type allocatorType = ByteBufferAllocator.Type.LARGE;
-        if (name.contains("segments") || name.endsWith(".del")) {
+        if (isSmallFile(name)) {
             allocatorType = ByteBufferAllocator.Type.SMALL;
         }
         ByteBufferFileOutput file = new ByteBufferFileOutput(this, allocator.sizeInBytes(allocatorType));
diff --git a/src/test/java/org/elasticsearch/index/engine/robin/RobinEngineIntegrationTest.java b/src/test/java/org/elasticsearch/index/engine/robin/RobinEngineIntegrationTest.java
index fd9f5515ce5..4fe20eb95a6 100644
--- a/src/test/java/org/elasticsearch/index/engine/robin/RobinEngineIntegrationTest.java
+++ b/src/test/java/org/elasticsearch/index/engine/robin/RobinEngineIntegrationTest.java
@@ -19,11 +19,15 @@
 
 package org.elasticsearch.index.engine.robin;
 
+import org.elasticsearch.action.admin.cluster.node.info.NodeInfo;
+import org.elasticsearch.action.admin.cluster.node.info.NodesInfoResponse;
 import org.elasticsearch.action.admin.indices.segments.IndexSegments;
 import org.elasticsearch.action.admin.indices.segments.IndexShardSegments;
 import org.elasticsearch.action.admin.indices.segments.IndicesSegmentResponse;
 import org.elasticsearch.action.admin.indices.segments.ShardSegments;
 import org.elasticsearch.common.settings.ImmutableSettings;
+import org.elasticsearch.common.unit.ByteSizeUnit;
+import org.elasticsearch.common.unit.ByteSizeValue;
 import org.elasticsearch.index.engine.Segment;
 import org.elasticsearch.index.query.QueryBuilders;
 import org.elasticsearch.test.AbstractIntegrationTest;
@@ -82,15 +86,22 @@ public class RobinEngineIntegrationTest extends AbstractIntegrationTest {
     }
     @Test
     public void test4093() {
+        cluster().ensureAtMostNumNodes(1); // only one node Netty uses lots of native mem as well
         assertAcked(prepareCreate("test").setSettings(ImmutableSettings.settingsBuilder()
                 .put("index.store.type", "memory")
+                .put("cache.memory.large_cache_size", new ByteSizeValue(10, ByteSizeUnit.MB)) // no need to cache a lot
                 .put("index.number_of_shards", "1")
                 .put("index.number_of_replicas", "0")
                 .put("gateway.type", "none")
-                .put("http.enabled", false)
                 .put(RobinEngine.INDEX_COMPOUND_ON_FLUSH, randomBoolean())
                 .put("index.warmer.enabled", false)
                 .build()).get());
+        NodesInfoResponse nodeInfos = client().admin().cluster().prepareNodesInfo().setJvm(true).get();
+        NodeInfo[] nodes = nodeInfos.getNodes();
+        for (NodeInfo info : nodes) {
+            ByteSizeValue directMemoryMax = info.getJvm().getMem().getDirectMemoryMax();
+            logger.info(" JVM max direct memory for node [{}] is set to [{}]", info.getNode().getName(), directMemoryMax);
+        }
         final int iters = between(500, 1000);
         for (int i = 0; i < iters; i++) {
             client().prepareIndex("test", "type1")
@@ -99,6 +110,7 @@ public class RobinEngineIntegrationTest extends AbstractIntegrationTest {
                     .execute()
                     .actionGet();
         }
+
         assertHitCount(client().prepareCount("test").setQuery(QueryBuilders.matchAllQuery()).get(), iters);
     }
 }
diff --git a/src/test/java/org/elasticsearch/test/TestCluster.java b/src/test/java/org/elasticsearch/test/TestCluster.java
index f0ce94bbb2f..2756ba8bde1 100644
--- a/src/test/java/org/elasticsearch/test/TestCluster.java
+++ b/src/test/java/org/elasticsearch/test/TestCluster.java
@@ -217,14 +217,19 @@ public class TestCluster implements Closeable, Iterable<Client> {
         if (nodes.size() <= num) {
             return;
         }
-        Collection<NodeAndClient> values = nodes.values();
-        Iterator<NodeAndClient> limit = Iterators.limit(values.iterator(), nodes.size() - num);
+        // prevent killing the master if possible
+        final Iterator<NodeAndClient> values = num == 0 ? nodes.values().iterator() : Iterators.filter(nodes.values().iterator(), Predicates.not(new MasterNodePredicate(getMasterName())));
+        final Iterator<NodeAndClient> limit = Iterators.limit(values, nodes.size() - num);
         logger.info("reducing cluster size from {} to {}", nodes.size() - num, num);
+        Set<NodeAndClient> nodesToRemove = new HashSet<NodeAndClient>();
         while (limit.hasNext()) {
             NodeAndClient next = limit.next();
-            limit.remove();
+            nodesToRemove.add(next);
             next.close();
         }
+        for (NodeAndClient toRemove : nodesToRemove) {
+            nodes.remove(toRemove.name);
+        }
     }
 
     private NodeAndClient buildNode(Settings settings) {