[OpenAFS] About openafs discon mode

Jeffrey Hutzelman jhutz@cmu.edu
Fri, 20 Dec 2013 15:53:22 -0500

On Fri, 2013-12-20 at 20:11 +0100, nicolas prochazka wrote:
> ok,
> so discon mode cannot work ?

I didn't say that.  However, as it turns out, the cache manager appears
to be discarding volume-level information, such as the name-to-id
mappings you need to evaluate mount points.  What this means is that
traversing mount points may not work after a while.  As far as I can
tell from a quick examination of the relevant code, this is a real bug
for which the fix will be nontrivial.

> and is it possible to define callback expiration time ?  ( hacking code is
> a solution for me, 2h=>24h)

You can have the fileserver give out longer callbacks, but I don't
recommend significant increases unless your cell has a very small number
of clients.  Callback expiration is designed to bound the amount of data
the fileserver needs to keep about outstanding callbacks, and increasing
that bound will affect the server's memory usage.

In practice, it looks like the problem you're seeing is likely related
to the expiration of whole-volume callbacks on readonly volumes.  You
may be able to increase the whole-volume callback time beyond the
default 2 hours, but again, I'd be careful about this.  It's not
necessary for online operation, and will have an effect on server memory

-- Jeff