diff --git a/includes/file.inc b/includes/file.inc
index bbcf9dc..c6887bd 100644
--- a/includes/file.inc
+++ b/includes/file.inc
@@ -273,7 +273,34 @@ function file_copy(&$source, $dest = 0, $replace = FILE_EXISTS_RENAME) {
       return FALSE;
     }
 
-    if (!@copy($source, $dest)) {
+    // Perform the replace operation. Since there could be multiple processes
+    // writing to the same file, the best option is to create a temporary file in
+    // the same directory and then rename it to the destination. A temporary file
+    // is needed if the directory is mounted on a separate machine; thus ensuring
+    // the rename command stays local.
+    $result = FALSE;
+    if ($replace == FILE_EXISTS_REPLACE) {
+      // Get a temporary filename in the destination directory.
+      $temporary_file = tempnam(dirname($dest), 'file');
+      // Place contents in the temporary file.
+      if ($temporary_file && @copy($source, $temporary_file)) {
+        if (!$result = @rename($temporary_file, $dest)) {
+          // Unlink and try again for windows. Rename on windows does not replace
+          // the file if it already exists.
+          @unlink($dest);
+          $result = @rename($temporary_file, $dest);
+        }
+        // Remove temporary_file if rename failed.
+        if (!$result) {
+          @unlink($temporary_file);
+        }
+      }
+    }
+    // Perform the copy operation.
+    else {
+      $result = @copy($source, $dest);
+    }
+    if ($result === FALSE) {
       drupal_set_message(t('The selected file %file could not be copied.', array('%file' => $source)), 'error');
       return 0;
     }
@@ -831,7 +858,7 @@ function file_save_data($data, $dest, $replace = FILE_EXISTS_RENAME) {
 /**
  * Set the status of a file.
  *
- * @param $file 
+ * @param $file
  *   A Drupal file object.
  * @param $status
  *   A status value to set the file to. One of:
@@ -860,7 +887,7 @@ function file_transfer($source, $headers) {
   if (ob_get_level()) {
     ob_end_clean();
   }
-  
+
   // IE cannot download private files because it cannot store files downloaded
   // over https in the browser cache. The problem can be solved by sending
   // custom headers to IE. See http://support.microsoft.com/kb/323308/en-us