diff --git a/doc/src/sgml/pgupgrade.sgml b/doc/src/sgml/pgupgrade.sgml
new file mode 100644
index 3d529b2..bb3b6a0
*** a/doc/src/sgml/pgupgrade.sgml
--- b/doc/src/sgml/pgupgrade.sgml
*************** psql --username postgres --file script.s
*** 569,575 ****
     the old server and run <command>rsync</> again to update the copy with any
     changes to make it consistent.  You might want to exclude some
     files, e.g. <filename>postmaster.pid</>, as documented in <xref
!    linkend="backup-lowlevel-base-backup">.
    </para>
  
   <refsect2>
--- 569,578 ----
     the old server and run <command>rsync</> again to update the copy with any
     changes to make it consistent.  You might want to exclude some
     files, e.g. <filename>postmaster.pid</>, as documented in <xref
!    linkend="backup-lowlevel-base-backup">.  If your file system supports
!    file system snapshots or copy-on-write file copying, you can use that
!    to make a backup of the old cluster, though the snapshot and copies
!    must be created simultaneously or while the database server is down.
    </para>
  
   <refsect2>