And this one

Author: thecoop

server/src/internalClusterTest/java/org/elasticsearch/index/store/DirectIOIT.java

@@ -17,6 +17,7 @@
 import org.apache.lucene.store.IndexOutput;
 import org.apache.lucene.tests.util.LuceneTestCase;
 import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.index.codec.vectors.es818.ES818BinaryQuantizedVectorsFormat;
 import org.elasticsearch.plugins.Plugin;
 import org.elasticsearch.search.vectors.KnnSearchBuilder;
 import org.elasticsearch.search.vectors.VectorData;
@@ -46,6 +47,7 @@ public class DirectIOIT extends ESIntegTestCase {
 
     @BeforeClass
     public static void checkSupported() throws IOException {
+        assumeTrue("test requires direct IO", ES818BinaryQuantizedVectorsFormat.USE_DIRECT_IO);
         Path path = createTempDir("directIOProbe");
         try (Directory dir = open(path); IndexOutput out = dir.createOutput("out", IOContext.DEFAULT)) {
             out.writeString("test");

server/src/main/java/org/elasticsearch/index/codec/vectors/es818/ES818BinaryQuantizedVectorsFormat.java

@@ -87,7 +87,7 @@
  */
 public class ES818BinaryQuantizedVectorsFormat extends FlatVectorsFormat {
 
-    static final boolean USE_DIRECT_IO = Boolean.parseBoolean(System.getProperty("vector.rescoring.directio", "false"));
+    public static final boolean USE_DIRECT_IO = Boolean.parseBoolean(System.getProperty("vector.rescoring.directio", "false"));
 
     public static final String BINARIZED_VECTOR_COMPONENT = "BVEC";
     public static final String NAME = "ES818BinaryQuantizedVectorsFormat";