LUDOC-11 changelog: describe changelog space usage

Clarify under changelog registration that this consumes space on the
MDT, and if there is no changelog user that this can fill all space
on the MDT eventually.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: I4f216a77a66e2f4b17d2c2378112f57dfd7e5f2d
Reviewed-on: http://review.whamcloud.com/23097
Tested-by: Jenkins
Reviewed-by: Joseph Gmitter <joseph.gmitter@intel.com>

diff --git a/SystemConfigurationUtilities.xml b/SystemConfigurationUtilities.xml
index 40a179d..b3c1fc7 100644 (file)
--- a/SystemConfigurationUtilities.xml
+++ b/SystemConfigurationUtilities.xml
@@ -601,7 +601,14 @@ $ lctl conf_param testfs.llite.max_read_ahead_mb=16 </screen>
                 <para> <literal>changelog_register</literal></para>
               </entry>
               <entry>
-                <para> Registers a new changelog user for a particular device. Changelog entries are not purged beyond a registered user&apos;s set point (see <literal>lfs changelog_clear</literal>).</para>
+                <para> Registers a new changelog user for a particular device.
+               Changelog entries are saved persistently on the MDT with each
+               filesystem operation, and are only purged beyond all registered
+               user&apos;s minimum set point (see
+               <literal>lfs changelog_clear</literal>). This may cause the
+               Changelog to consume a large amount of space, eventually
+               filling the MDT, if a changelog user is registered but never
+               consumes those records.</para>
               </entry>
             </row>
             <row>
@@ -609,7 +616,10 @@ $ lctl conf_param testfs.llite.max_read_ahead_mb=16 </screen>
                 <para>changelog_deregister <replaceable>id</replaceable></para>
               </entry>
               <entry>
-                <para> Unregisters an existing changelog user. If the user&apos;s &quot;clear&quot; record number is the minimum for the device, changelog records are purged until the next minimum.</para>
+                <para> Unregisters an existing changelog user. If the
+               user&apos;s &quot;clear&quot; record number is the minimum for
+               the device, changelog records are purged until the next minimum.
+               </para>
               </entry>
             </row>
           </tbody>