Index: library/Zend/Cache/Backend/File.php
===================================================================
--- library/Zend/Cache/Backend/File.php (revision 24626)
+++ library/Zend/Cache/Backend/File.php (working copy)
@@ -71,7 +71,8 @@
      * for you. Maybe, 1 or 2 is a good start.
      *
      * =====> (int) hashed_directory_umask :
-     * - Umask for hashed directory structure
+     * - Mode to chmod hashed directory structure to
+     *   NOTE: ensure you use an octal file mode (chmod) and not a umask value
      *
      * =====> (string) file_name_prefix :
      * - prefix for cache files
@@ -79,7 +80,8 @@
      *   (like /tmp) can cause disasters when cleaning the cache
      *
      * =====> (int) cache_file_umask :
-     * - Umask for cache files
+     * - Mode to chmod cache files to
+     *   NOTE: ensure you use an octal file mode (chmod) and not a umask value
      *
      * =====> (int) metatadatas_array_max_size :
      * - max size for the metadatas array (don't change this value unless you
Index: documentation/manual/en/module_specs/Zend_Cache-Backends.xml
===================================================================
--- documentation/manual/en/module_specs/Zend_Cache-Backends.xml        (revision 24626)
+++ documentation/manual/en/module_specs/Zend_Cache-Backends.xml        (working copy)
@@ -95,7 +95,7 @@
                         <entry><emphasis>hashed_directory_umask</emphasis></entry>
                         <entry><type>Integer</type></entry>
                         <entry>0700</entry>
-                        <entry>Umask for the hashed directory structure</entry>
+                        <entry>Mode that directories in the hashed directory structure are <ulink url="http://php.net/chmod">chmod</ulink>ed to</entry>
                     </row>

                     <row>
@@ -115,7 +115,7 @@
                         <entry><emphasis>cache_file_umask</emphasis></entry>
                         <entry><type>Integer</type></entry>
                         <entry>0600</entry>
-                        <entry>umask for cache files</entry>
+                        <entry>Mode that cache files are <ulink url="http://php.net/chmod">chmod</ulink>ed to</entry>
                     </row>

                     <row>
@@ -131,6 +131,13 @@
                 </tbody>
             </tgroup>
         </table>
+
+        <note>
+            <title>A note about cache_file_umask and hashed_directory_umask</title>
+            <para>
+                Despite having 'umask' in their names, these options set the octal file mode which will be passed to the <ulink url="http://php.net/chmod">chmod PHP function</ulink>.  Be aware that you are not mistakenly passing a <ulink url="http://php.net/umask">umask</ulink> value, which is the inverse of the file mode.  The file mode defines the permissions to grant, whereas umask defines the permissions <emphasis>not</emphasis> to grant.
+            </para>
+        </note>
     </sect2>

     <sect2 id="zend.cache.backends.sqlite">