diff --git a/CHANGES.txt b/CHANGES.txt
index 74cbbf9b00..e7a38914fb 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -5,6 +5,7 @@
 
 
 5.0-rc2
+ * Fix direct IO support always being evaluated to false upon the first start of a node (CASSANDRA-19779)
 
 
 5.0-rc1
diff --git a/src/java/org/apache/cassandra/config/DatabaseDescriptor.java b/src/java/org/apache/cassandra/config/DatabaseDescriptor.java
index 61d4a44adb..388b4b7f30 100644
--- a/src/java/org/apache/cassandra/config/DatabaseDescriptor.java
+++ b/src/java/org/apache/cassandra/config/DatabaseDescriptor.java
@@ -17,6 +17,7 @@
  */
 package org.apache.cassandra.config;
 
+import java.io.IOError;
 import java.io.IOException;
 import java.lang.management.ManagementFactory;
 import java.lang.management.RuntimeMXBean;
@@ -1456,7 +1457,18 @@ public class DatabaseDescriptor
         boolean directIOSupported = false;
         try
         {
-            directIOSupported = FileUtils.getBlockSize(new File(getCommitLogLocation())) > 0;
+            String commitLogLocation = getCommitLogLocation();
+
+            if (commitLogLocation == null)
+                throw new ConfigurationException("commitlog_directory must be specified", false);
+
+            File commitLogLocationDir = new File(commitLogLocation);
+            PathUtils.createDirectoriesIfNotExists(commitLogLocationDir.toPath());
+            directIOSupported = FileUtils.getBlockSize(commitLogLocationDir) > 0;
+        }
+        catch (IOError | ConfigurationException ex)
+        {
+            throw  ex;
         }
         catch (RuntimeException e)
         {
@@ -2844,6 +2856,7 @@ public class DatabaseDescriptor
     @VisibleForTesting
     public static void setCommitLogWriteDiskAccessMode(DiskAccessMode diskAccessMode)
     {
+        commitLogWriteDiskAccessMode = diskAccessMode;
         conf.commitlog_disk_access_mode = diskAccessMode;
     }
 
diff --git a/test/unit/org/apache/cassandra/config/DatabaseDescriptorTest.java b/test/unit/org/apache/cassandra/config/DatabaseDescriptorTest.java
index bc51e73601..b624698bd6 100644
--- a/test/unit/org/apache/cassandra/config/DatabaseDescriptorTest.java
+++ b/test/unit/org/apache/cassandra/config/DatabaseDescriptorTest.java
@@ -38,9 +38,12 @@ import org.junit.Test;
 import org.apache.cassandra.db.Keyspace;
 import org.apache.cassandra.distributed.shared.WithProperties;
 import org.apache.cassandra.exceptions.ConfigurationException;
+import org.apache.cassandra.io.util.FileUtils;
+import org.apache.cassandra.io.util.PathUtils;
 import org.apache.cassandra.security.EncryptionContext;
 import org.apache.cassandra.security.EncryptionContextGenerator;
 import org.assertj.core.api.Assertions;
+import org.mockito.MockedStatic;
 
 import static org.apache.cassandra.config.CassandraRelevantProperties.ALLOW_UNLIMITED_CONCURRENT_VALIDATIONS;
 import static org.apache.cassandra.config.CassandraRelevantProperties.CONFIG_LOADER;
@@ -52,6 +55,8 @@ import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mockStatic;
 
 public class DatabaseDescriptorTest
 {
@@ -849,31 +854,36 @@ public class DatabaseDescriptorTest
             assertCommitLogDiskAccessModes(Config.DiskAccessMode.standard, Config.DiskAccessMode.standard, Config.DiskAccessMode.standard);
 
             // block size not available
-            DatabaseDescriptor.setCommitLogLocation(null);
+            try (MockedStatic<FileUtils> fileUtilsMock = mockStatic(FileUtils.class);
+                 MockedStatic<PathUtils> pathUtilsMock = mockStatic(PathUtils.class))
+            {
+                pathUtilsMock.when(() -> PathUtils.createDirectoriesIfNotExists(any())).thenAnswer(invocation -> null);
+                fileUtilsMock.when(() -> FileUtils.getBlockSize(any())).thenThrow(new RuntimeException("unable to get block size"));
 
-            // no encryption or compression
-            DatabaseDescriptor.setCommitLogCompression(null);
-            DatabaseDescriptor.setEncryptionContext(null);
-            DatabaseDescriptor.getRawConfig().disk_optimization_strategy = Config.DiskOptimizationStrategy.spinning;
-            assertCommitLogDiskAccessModes(Config.DiskAccessMode.mmap, Config.DiskAccessMode.mmap, Config.DiskAccessMode.mmap, Config.DiskAccessMode.direct);
-            DatabaseDescriptor.getRawConfig().disk_optimization_strategy = Config.DiskOptimizationStrategy.ssd;
-            assertCommitLogDiskAccessModes(Config.DiskAccessMode.mmap, Config.DiskAccessMode.mmap, Config.DiskAccessMode.mmap, Config.DiskAccessMode.direct);
+                // no encryption or compression
+                DatabaseDescriptor.setCommitLogCompression(null);
+                DatabaseDescriptor.setEncryptionContext(null);
+                DatabaseDescriptor.getRawConfig().disk_optimization_strategy = Config.DiskOptimizationStrategy.spinning;
+                assertCommitLogDiskAccessModes(Config.DiskAccessMode.mmap, Config.DiskAccessMode.mmap, Config.DiskAccessMode.mmap, Config.DiskAccessMode.direct);
+                DatabaseDescriptor.getRawConfig().disk_optimization_strategy = Config.DiskOptimizationStrategy.ssd;
+                assertCommitLogDiskAccessModes(Config.DiskAccessMode.mmap, Config.DiskAccessMode.mmap, Config.DiskAccessMode.mmap, Config.DiskAccessMode.direct);
 
-            // compression enabled
-            DatabaseDescriptor.setCommitLogCompression(new ParameterizedClass("LZ4Compressor", null));
-            DatabaseDescriptor.setEncryptionContext(null);
-            DatabaseDescriptor.getRawConfig().disk_optimization_strategy = Config.DiskOptimizationStrategy.spinning;
-            assertCommitLogDiskAccessModes(Config.DiskAccessMode.standard, Config.DiskAccessMode.standard, Config.DiskAccessMode.standard);
-            DatabaseDescriptor.getRawConfig().disk_optimization_strategy = Config.DiskOptimizationStrategy.ssd;
-            assertCommitLogDiskAccessModes(Config.DiskAccessMode.standard, Config.DiskAccessMode.standard, Config.DiskAccessMode.standard);
+                // compression enabled
+                DatabaseDescriptor.setCommitLogCompression(new ParameterizedClass("LZ4Compressor", null));
+                DatabaseDescriptor.setEncryptionContext(null);
+                DatabaseDescriptor.getRawConfig().disk_optimization_strategy = Config.DiskOptimizationStrategy.spinning;
+                assertCommitLogDiskAccessModes(Config.DiskAccessMode.standard, Config.DiskAccessMode.standard, Config.DiskAccessMode.standard);
+                DatabaseDescriptor.getRawConfig().disk_optimization_strategy = Config.DiskOptimizationStrategy.ssd;
+                assertCommitLogDiskAccessModes(Config.DiskAccessMode.standard, Config.DiskAccessMode.standard, Config.DiskAccessMode.standard);
 
-            // encryption enabled
-            DatabaseDescriptor.setCommitLogCompression(null);
-            DatabaseDescriptor.setEncryptionContext(new EncryptionContext(EncryptionContextGenerator.createEncryptionOptions()));
-            DatabaseDescriptor.getRawConfig().disk_optimization_strategy = Config.DiskOptimizationStrategy.spinning;
-            assertCommitLogDiskAccessModes(Config.DiskAccessMode.standard, Config.DiskAccessMode.standard, Config.DiskAccessMode.standard);
-            DatabaseDescriptor.getRawConfig().disk_optimization_strategy = Config.DiskOptimizationStrategy.ssd;
-            assertCommitLogDiskAccessModes(Config.DiskAccessMode.standard, Config.DiskAccessMode.standard, Config.DiskAccessMode.standard);
+                // encryption enabled
+                DatabaseDescriptor.setCommitLogCompression(null);
+                DatabaseDescriptor.setEncryptionContext(new EncryptionContext(EncryptionContextGenerator.createEncryptionOptions()));
+                DatabaseDescriptor.getRawConfig().disk_optimization_strategy = Config.DiskOptimizationStrategy.spinning;
+                assertCommitLogDiskAccessModes(Config.DiskAccessMode.standard, Config.DiskAccessMode.standard, Config.DiskAccessMode.standard);
+                DatabaseDescriptor.getRawConfig().disk_optimization_strategy = Config.DiskOptimizationStrategy.ssd;
+                assertCommitLogDiskAccessModes(Config.DiskAccessMode.standard, Config.DiskAccessMode.standard, Config.DiskAccessMode.standard);
+            }
         }
         finally
         {
diff --git a/test/unit/org/apache/cassandra/repair/FuzzTestBase.java b/test/unit/org/apache/cassandra/repair/FuzzTestBase.java
index b389231c68..1644c6fb74 100644
--- a/test/unit/org/apache/cassandra/repair/FuzzTestBase.java
+++ b/test/unit/org/apache/cassandra/repair/FuzzTestBase.java
@@ -70,6 +70,7 @@ import org.apache.cassandra.concurrent.ScheduledExecutorPlus;
 import org.apache.cassandra.concurrent.SequentialExecutorPlus;
 import org.apache.cassandra.concurrent.SimulatedExecutorFactory;
 import org.apache.cassandra.concurrent.Stage;
+import org.apache.cassandra.config.Config;
 import org.apache.cassandra.config.DatabaseDescriptor;
 import org.apache.cassandra.config.UnitConfigOverride;
 import org.apache.cassandra.cql3.CQLTester;
@@ -182,6 +183,8 @@ public abstract class FuzzTestBase extends CQLTester.InMemory
         UnitConfigOverride.maybeOverrideConfig();
 
         DatabaseDescriptor.daemonInitialization();
+        DatabaseDescriptor.setCommitLogWriteDiskAccessMode(Config.DiskAccessMode.mmap);
+
         DatabaseDescriptor.setPartitionerUnsafe(Murmur3Partitioner.instance); // TOOD (coverage): random select
         DatabaseDescriptor.setLocalDataCenter("test");
         StreamingChannel.Factory.Global.unsafeSet(new StreamingChannel.Factory()