title: otherwise working munin not showing graph when node is offline
body: <p>I have a working munin setup that is plotting graphs for around 50 machines. The machines are connected via a somewhat brittle umts connection. Whenever one of the machines goes down the (historic) graphs are replaced by "Image not found"-placeholders. This eliminates the graphs as a source of information on why the machine went down.</p>
  
  <p>On the munin irc i was told that this is expected behavior and that I should run munin-asyncd to buffer the values. I don't understand however how this would solve my problem. As far as I understand it would introduce some delay but not fundamentally change anything.</p>
  
  <p>Also the graphs are still in ''/var/lib/munin'' but copying them from there every time and plotting manually with rrdtool is cumbersome. So is there some configuration switch to make munin show the graphs even when the machine down? </p>