Index: src/java/org/apache/lucene/store/FSDirectory.java
===================================================================
--- src/java/org/apache/lucene/store/FSDirectory.java	(revision 591752)
+++ src/java/org/apache/lucene/store/FSDirectory.java	(working copy)
@@ -62,6 +62,8 @@
 
   private static boolean disableLocks = false;
 
+  private boolean doSync = false;
+
   // TODO: should this move up to the Directory base class?  Also: should we
   // make a per-instance (in addition to the static "default") version?
 
@@ -136,33 +138,67 @@
    * @return the FSDirectory for the named file.  */
   public static FSDirectory getDirectory(String path)
       throws IOException {
-    return getDirectory(new File(path), null);
+    return getDirectory(new File(path), null, false);
   }
 
   /** Returns the directory instance for the named location.
    * @param path the path to the directory.
    * @param lockFactory instance of {@link LockFactory} providing the
-   *        locking implementation.
+   *        locking implementation.  If null, the default
+   *        {@link SimpleFSLockFactory} is used.
    * @return the FSDirectory for the named file.  */
   public static FSDirectory getDirectory(String path, LockFactory lockFactory)
       throws IOException {
-    return getDirectory(new File(path), lockFactory);
+    return getDirectory(new File(path), lockFactory, false);
   }
 
   /** Returns the directory instance for the named location.
+   * @param path the path to the directory.
+   * @param lockFactory instance of {@link LockFactory} providing the
+   *        locking implementation.  If null, the default
+   *        {@link SimpleFSLockFactory} is used.
+   * @param doSync if true, sync() is called on all file
+   *        descriptors before close().  This improves the
+   *        likelihood that the index will remain consistent
+   *        even if the JVM, OS or machine crashes.  Note
+   *        that this may slow down indexing.
+   * @return the FSDirectory for the named file.  */
+  public static FSDirectory getDirectory(String path, LockFactory lockFactory, boolean doSync)
+      throws IOException {
+    return getDirectory(new File(path), lockFactory, doSync);
+  }
+
+  /** Returns the directory instance for the named location.
    * @param file the path to the directory.
    * @return the FSDirectory for the named file.  */
   public static FSDirectory getDirectory(File file)
     throws IOException {
-    return getDirectory(file, null);
+    return getDirectory(file, null, false);
   }
 
   /** Returns the directory instance for the named location.
    * @param file the path to the directory.
    * @param lockFactory instance of {@link LockFactory} providing the
-   *        locking implementation.
+   *        locking implementation.  If null, the default
+   *        {@link SimpleFSLockFactory} is used.
    * @return the FSDirectory for the named file.  */
   public static FSDirectory getDirectory(File file, LockFactory lockFactory)
+      throws IOException {
+    return getDirectory(file, lockFactory, false);
+  }
+
+  /** Returns the directory instance for the named location.
+   * @param file the path to the directory.
+   * @param lockFactory instance of {@link LockFactory} providing the
+   *        locking implementation.  If null, the default
+   *        {@link SimpleFSLockFactory} is used.
+   * @param doSync if true, sync() is called on all file
+   *        descriptors before close().  This improves the
+   *        likelihood that the index will remain consistent
+   *        even if the JVM, OS or machine crashes.  Note
+   *        that this may slow down indexing.
+   * @return the FSDirectory for the named file.  */
+  public static FSDirectory getDirectory(File file, LockFactory lockFactory, boolean doSync)
     throws IOException
   {
     file = new File(file.getCanonicalPath());
@@ -183,7 +219,7 @@
         } catch (Exception e) {
           throw new RuntimeException("cannot load FSDirectory class: " + e.toString(), e);
         }
-        dir.init(file, lockFactory);
+        dir.init(file, lockFactory, doSync);
         DIRECTORIES.put(file, dir);
       } else {
         // Catch the case where a Directory is pulled from the cache, but has a
@@ -254,7 +290,7 @@
 
   protected FSDirectory() {};                     // permit subclassing
 
-  private void init(File path, LockFactory lockFactory) throws IOException {
+  private void init(File path, LockFactory lockFactory, boolean doSync) throws IOException {
 
     // Set up lockFactory with cascaded defaults: if an instance was passed in,
     // use that; else if locks are disabled, use NoLockFactory; else if the
@@ -262,6 +298,7 @@
     // instantiate that; else, use SimpleFSLockFactory:
 
     directory = path;
+    this.doSync = doSync;
 
     boolean doClearLockID = false;
 
@@ -432,7 +469,7 @@
     if (file.exists() && !file.delete())          // delete existing, if any
       throw new IOException("Cannot overwrite: " + file);
 
-    return new FSIndexOutput(file);
+    return new FSIndexOutput(file, doSync);
   }
 
   // Inherit javadoc
@@ -588,10 +625,13 @@
     // remember if the file is open, so that we don't try to close it
     // more than once
     private boolean isOpen;
-  
-    public FSIndexOutput(File path) throws IOException {
+    private boolean doSync;
+
+    public FSIndexOutput(File path, boolean doSync) throws IOException {
       file = new RandomAccessFile(path, "rw");
+
       isOpen = true;
+      this.doSync = doSync;
     }
   
     /** output methods: */
@@ -602,6 +642,8 @@
       // only close the file if it has not been closed yet
       if (isOpen) {
         super.close();
+        if (doSync)
+          file.getFD().sync();
         file.close();
         isOpen = false;
       }
Index: contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/PerfRunData.java
===================================================================
--- contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/PerfRunData.java	(revision 591752)
+++ contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/PerfRunData.java	(working copy)
@@ -126,7 +126,8 @@
         FileUtils.fullyDelete(indexDir);
       }
       indexDir.mkdirs();
-      directory = FSDirectory.getDirectory(indexDir);
+      final boolean doSync = config.get("fsdirectory.dosync", false);
+      directory = FSDirectory.getDirectory(indexDir, null, doSync);
     } else {
       directory = new RAMDirectory();
     }
Index: contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/package.html
===================================================================
--- contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/package.html	(revision 591752)
+++ contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/package.html	(working copy)
@@ -479,6 +479,12 @@
     </li>
 
     <li>
+    <font color="#FF0066">fsdirectory.dosync</font> - true/false
+    If "true", the FSDirectory will call sync() before close() on each
+    file.
+    </li>
+
+    <li>
     <b>Index work parameters</b>:
     Multi int/boolean values would be iterated with calls to NewRound.
     There would be also added as columns in the reports, first string in the
@@ -543,6 +549,7 @@
     </li><li>merge.factor
     </li><li>max.buffered
     </li><li>directory
+    </li><li>fsdirectory.dosync
     </li><li>ram.flush.mb
     </li><li>autocommit
     </li></ul>
@@ -676,4 +683,4 @@
 </DIV>
 <DIV>&nbsp;</DIV>
 </BODY>
-</HTML>
\ No newline at end of file
+</HTML>