[4.0] 57d2e7a Update the users guide to for new -sfile syntax

[Martin Blix Grydeland]

commit 57d2e7a8dedd214fee2ecae436bcfe4d67d228e9
Author: Martin Blix Grydeland <martin at varnish-software.com>
Date:   Mon Jun 1 14:19:05 2015 +0200

    Update the users guide to for new -sfile syntax
    
    It used to be possible to specify -sfile size in percentage. This
    feature has been removed. Update the users guide to reflect this.
    
    Fixes: #1744

diff --git a/doc/sphinx/users-guide/storage-backends.rst b/doc/sphinx/users-guide/storage-backends.rst
index 6664d8d..3539174 100644
--- a/doc/sphinx/users-guide/storage-backends.rst
+++ b/doc/sphinx/users-guide/storage-backends.rst
@@ -69,10 +69,9 @@ suffixes:
 
       T, t    The size is expressed in tebibytes.
 
-      %       The size is expressed as a percentage of the free space on the
-              file system where it resides.
-
-The default size is to use 50% of the space available on the device.
+If 'path' points to an existing file and no size is specified, the
+size of the existing file will be used. If 'path' does not point to an
+existing file it is an error to not specify the size.
 
 If the backing file already exists, it will be truncated or expanded
 to the specified size.