[OpenAFS] Disconnected OpenAFS

Jim Rees rees@umich.edu
Mon, 24 Sep 2007 23:07:13 -0400

Simon Wilkinson wrote:

  *) Data consistency is interesting. If a server breaks a callback, no  
  attempt is made to update the clients cache. If the client  
  subsequently goes disconnected, then that cached data will be made  
  available to the client, regardless of how the data on the server  
  changed. This is definitely sub-optimal.

I think you're being way too conservative here.  To provide the kind of
guarantee you are suggesting you would need to obtain and return callbacks
on everything in your cache before you disconnect.  That could be thousands
of files.  Most servers won't give you that many callbacks simultaneously so
you would be open to races.  Disconnection would take a long time and
present a large load on the server.  And you would be unable to go into
disconnected mode if the network unexpectedly went away, thereby losing one
of the nicest features of disconnected mode.