[OpenAFS] AFS design question: implementing AFS over a highly-distributed, low-bandwidth network

Simon Wilkinson sxw@inf.ed.ac.uk
Fri, 16 Jan 2009 14:26:01 +0000

On 16 Jan 2009, at 14:13, Jason Edgecombe wrote:

> Chaz Chandler wrote:
>>> Something that might work out a little better is the work being done
>>> on disconnected operation.  That might suffice for some of your use
>>> cases (assuming the timing of that finishing and the features it  
>>> will
>>> offer is suitable for your needs).
>> Is disconnected afs functional?  I saw it as a GSoC '08 project but  
>> the afsbpw08 presentation said it's only R/O.

The BPW presentation predates the work that Dragos did as part of  
Summer of Code. His project was very successful, and delivered a  
working disconnected client implementation which is now in the 1.5.x  
tree for testing.

> I would not inflict it upon any of my power users or regular users.  
> R/W
> does work, but rebooting will lose data and it doesn't work on  
> windows,
> just Unix. Simon can tell you more.

There's a couple of bits of major functionality missing, and some bugs  
which still need to be ironed out. In the functionality stakes, we  
currently don't preserve some important information when the machine  
is rebooted, so you lose any changes made whilst disconnected if you  
restart the machine without reconnecting. Less seriously, but still an  
issue, is that there's no mechanism for telling the cache manager  
which files you'd like to have available whilst disconnected. At  
present, you need to explicitly access every file and directory you  
require before disconnecting.

We're also still in bug hunting mode. There are some bugs with the  
disconnected implementation which are being found and fixed, and there  
are some race conditions in the cache manager which are being exposed  
by the differences in timing and serialisation when you are