diff --git a/lucene/src/java/org/apache/lucene/index/IndexWriter.java b/lucene/src/java/org/apache/lucene/index/IndexWriter.java
index 61d9e9a7598..9af6c4a7de0 100644
--- a/lucene/src/java/org/apache/lucene/index/IndexWriter.java
+++ b/lucene/src/java/org/apache/lucene/index/IndexWriter.java
@@ -2151,7 +2151,8 @@ public class IndexWriter implements Closeable {
         }
         SegmentInfos sis = new SegmentInfos(codecs); // read infos from dir
         sis.read(dir, codecs);
-        Map<String, String> dsNames = new HashMap<String, String>();
+        final Set<String> dsFilesCopied = new HashSet<String>();
+        final Map<String, String> dsNames = new HashMap<String, String>();
         for (SegmentInfo info : sis) {
           assert !infos.contains(info): "dup info dir=" + info.dir + " name=" + info.name;
 
@@ -2160,7 +2161,7 @@ public class IndexWriter implements Closeable {
           String dsName = info.getDocStoreSegment();
 
           if (infoStream != null) {
-            message("addIndexes: process segment origName=" + info.name + " newName=" + newSegName + " dsName=" + dsName);
+            message("addIndexes: process segment origName=" + info.name + " newName=" + newSegName + " dsName=" + dsName + " info=" + info);
           }
 
           // Determine if the doc store of this segment needs to be copied. It's
@@ -2170,22 +2171,32 @@ public class IndexWriter implements Closeable {
           // NOTE: pre-3x segments include a null DSName if they don't share doc
           // store. So the following code ensures we don't accidentally insert
           // 'null' to the map.
-          String newDsName = newSegName;
-          boolean docStoreCopied = false;
-          if (dsNames.containsKey(dsName)) {
-            newDsName = dsNames.get(dsName);
-            docStoreCopied = true;
-          } else if (dsName != null) {
-            dsNames.put(dsName, newSegName);
-            docStoreCopied = false;
+          final String newDsName;
+          if (dsName != null) {
+            if (dsNames.containsKey(dsName)) {
+              newDsName = dsNames.get(dsName);
+            } else {
+              dsNames.put(dsName, newSegName);
+              newDsName = newSegName;
+            }
+          } else {
+            newDsName = newSegName;
           }
 
           // Copy the segment files
-          for (String file : info.files()) {
-            if (docStoreCopied && IndexFileNames.isDocStoreFile(file)) {
-              continue;
-            } 
-            dir.copy(directory, file, newSegName + IndexFileNames.stripSegmentName(file));
+          for (String file: info.files()) {
+            final String newFileName;
+            if (IndexFileNames.isDocStoreFile(file)) {
+              newFileName = newDsName + IndexFileNames.stripSegmentName(file);
+              if (dsFilesCopied.contains(newFileName)) {
+                continue;
+              }
+              dsFilesCopied.add(newFileName);
+            } else {
+              newFileName = newSegName + IndexFileNames.stripSegmentName(file);
+            }
+            assert !directory.fileExists(newFileName): "file \"" + newFileName + "\" already exists";
+            dir.copy(directory, file, newFileName);
           }
 
           // Update SI appropriately
diff --git a/lucene/src/java/org/apache/lucene/index/SegmentInfo.java b/lucene/src/java/org/apache/lucene/index/SegmentInfo.java
index f1ec386ff80..afb5f1744c7 100644
--- a/lucene/src/java/org/apache/lucene/index/SegmentInfo.java
+++ b/lucene/src/java/org/apache/lucene/index/SegmentInfo.java
@@ -581,6 +581,9 @@ public final class SegmentInfo {
     if (this.dir != dir) {
       s.append('x');
     }
+    if (hasVectors) {
+      s.append('v');
+    }
     s.append(docCount);
 
     int delCount = getDelCount() + pendingDelCount;
diff --git a/lucene/src/test/org/apache/lucene/index/TestIndexWriterMerging.java b/lucene/src/test/org/apache/lucene/index/TestIndexWriterMerging.java
index 804db65d15c..6278b52c42c 100644
--- a/lucene/src/test/org/apache/lucene/index/TestIndexWriterMerging.java
+++ b/lucene/src/test/org/apache/lucene/index/TestIndexWriterMerging.java
@@ -60,7 +60,7 @@ public class TestIndexWriterMerging extends LuceneTestCase
         newIndexWriterConfig(TEST_VERSION_CURRENT, new MockAnalyzer()).
             setMergePolicy(newLogMergePolicy(2))
     );
-
+    writer.setInfoStream(VERBOSE ? System.out : null);
     writer.addIndexes(indexA, indexB);
     writer.optimize();
     writer.close();
diff --git a/lucene/src/test/org/apache/lucene/index/TestIndexWriterOnDiskFull.java b/lucene/src/test/org/apache/lucene/index/TestIndexWriterOnDiskFull.java
index 6702612be97..5016f5245d4 100644
--- a/lucene/src/test/org/apache/lucene/index/TestIndexWriterOnDiskFull.java
+++ b/lucene/src/test/org/apache/lucene/index/TestIndexWriterOnDiskFull.java
@@ -209,7 +209,7 @@ public class TestIndexWriterOnDiskFull extends LuceneTestCase {
         System.out.println("TEST: iter=" + iter);
       
       // Start with 100 bytes more than we are currently using:
-      long diskFree = diskUsage+100;
+      long diskFree = diskUsage+_TestUtil.nextInt(random, 50, 200);
       
       int method = iter;
       
@@ -226,12 +226,16 @@ public class TestIndexWriterOnDiskFull extends LuceneTestCase {
       }
       
       while(!done) {
+        if (VERBOSE) {
+          System.out.println("TEST: cycle...");
+        }
         
         // Make a new dir that will enforce disk usage:
         MockDirectoryWrapper dir = new MockDirectoryWrapper(random, new RAMDirectory(startDir));
         writer = new IndexWriter(dir, newIndexWriterConfig( TEST_VERSION_CURRENT, new MockAnalyzer()).setOpenMode(OpenMode.APPEND));
         IOException err = null;
-        
+        writer.setInfoStream(VERBOSE ? System.out : null);
+
         MergeScheduler ms = writer.getConfig().getMergeScheduler();
         for(int x=0;x<2;x++) {
           if (ms instanceof ConcurrentMergeScheduler)