>the data available to the application as it obtains it. If the network goes
>away venus would have to simply remember that the file in question is
>incomplete and not allow changes to the file until the network was
>available again or the file completely retrieved.

The "problem" here is that once the file has been opened, venus is not
contacted for reads and writes.  All coda kernel modules redirect
reads and writes to the local file system on which the cache file is
stored WITHOUT contacting venus.  This makes reads and writes at local
disk speed.  Any kind of "partial file in cache" would require all
kernel modules to be rewritten to communicate with venus to be able
to verify if a read or write was OK before doing the read or write.

Hoard is the tool of choice here.  It makes sure your cache has the
files in the cache so an open() does not have to wait for your file
to be transferred over the network.  It is already in your cache.

--Phil 

-- 
Phil Nelson                       NetBSD: http://www.netbsd.org
e-mail: phil@cs.wwu.edu           Coda: http://www.coda.cs.cmu.edu
http://cs.wwu.edu/faculty/nelson