 class DiffSyncFile_server extends diffsync.DiffSync
     constructor:(@cm_session, cb)  ->
         @path = @cm_session.path
-        @_backup_file = misc.meta_file(@path, 'backup')
-        # check for need to save a backup every this many milliseconds
-        @_autosave = setInterval(@write_backup, 10000)
-
-        # We prefer the backup file only if it both (1) exists, and
-        # (2) is *newer* than the master file.  This is because some
-        # other editing program could have edited the master, not
-        # knowing about the backup, in which case it makes more sense
-        # to just go with the master.
 
         no_master    = undefined
         stats_path   = undefined
-        no_backup    = undefined
-        stats_backup = undefined
         stats        = undefined
         file         = undefined
 

                cb?(err); return
            fs.writeFile @path, @live, (err) =>
                @_start_watching_file()
                if not err
                    fs.exists @_backup_file, (exists) =>
                        fs.unlink(@_backup_file)
                cb?(err)

    write_backup: (cb) =>
        if @cm_session.content != @_last_backup
            x = @cm_session.content
            fs.writeFile @_backup_file, x, (err) =>
                if not err
                    @_last_backup = x
                cb?(err)



                                    cb(err)
                                else
                                    fs.close fd, cb
                else
                    # master exists
                    file = @path
                    stats = stats_path
                    cb()
            (cb) =>
                e = check_file_size(stats?.size)
