diff --git a/doc/source/configuration.rst b/doc/source/configuration.rst
index d932d8c..49cad05 100644
--- a/doc/source/configuration.rst
+++ b/doc/source/configuration.rst
@@ -667,7 +667,7 @@
 
         VOLUME_GROUP_NAME="stack-volumes"
         VOLUME_NAME_PREFIX="volume-"
-        VOLUME_BACKING_FILE_SIZE=10250M
+        VOLUME_BACKING_FILE_SIZE=24G
 
 
 Keystone