diff --git a/indexing-hadoop/src/main/java/io/druid/indexer/HadoopTuningConfig.java b/indexing-hadoop/src/main/java/io/druid/indexer/HadoopTuningConfig.java
index a93c7653964..be70ef462e5 100644
--- a/indexing-hadoop/src/main/java/io/druid/indexer/HadoopTuningConfig.java
+++ b/indexing-hadoop/src/main/java/io/druid/indexer/HadoopTuningConfig.java
@@ -38,7 +38,7 @@ public class HadoopTuningConfig implements TuningConfig
 {
   private static final PartitionsSpec defaultPartitionsSpec = HashedPartitionsSpec.makeDefaultHashedPartitionsSpec();
   private static final Map<DateTime, List<HadoopyShardSpec>> defaultShardSpecs = ImmutableMap.<DateTime, List<HadoopyShardSpec>>of();
-  private static final int defaultBufferSize = 256 * 1024 * 1024;
+  private static final int defaultBufferSize = 512 * 1024 * 1024;
 
   public static HadoopTuningConfig makeDefaultTuningConfig()
   {
diff --git a/server/src/main/java/io/druid/segment/indexing/RealtimeTuningConfig.java b/server/src/main/java/io/druid/segment/indexing/RealtimeTuningConfig.java
index 52df7cafbe4..29d93deb5a0 100644
--- a/server/src/main/java/io/druid/segment/indexing/RealtimeTuningConfig.java
+++ b/server/src/main/java/io/druid/segment/indexing/RealtimeTuningConfig.java
@@ -36,7 +36,7 @@ import java.io.File;
  */
 public class RealtimeTuningConfig implements TuningConfig
 {
-  private static final int defaultBufferSize = 256 * 1024 * 1024;
+  private static final int defaultBufferSize = 512 * 1024 * 1024;
   private static final Period defaultIntermediatePersistPeriod = new Period("PT10M");
   private static final Period defaultWindowPeriod = new Period("PT10M");
   private static final File defaultBasePersistDirectory = Files.createTempDir();