[OpenAFS] Re: Afs User volume servers in VM's

Andrew Deason adeason@sinenomine.net
Wed, 26 Oct 2011 12:16:03 -0500

On Wed, 26 Oct 2011 18:41:15 +0200
Stephan Wiesand <stephan.wiesand@desy.de> wrote:

> > However, the way to do that is to return a VBUSY error to the client
> > ("busy; try again later"),
> Well, isn't this the right answer in that situation?

I don't know; I think it depends on the workload. I'm not saying that's
going to stop me or whomever from implementing it (sometime), just that
it may not be the miracle cure you're looking for.

> Booker and me would probably be ok with errors being returned upon
> access to a single volume that's being overwhelmed with I/O requests -
> if it just wouldn't make the fileserver as a whole grind to a halt and
> not service any request any more.

Well, see, it depends on _what_ is causing it to do that, as Jeffrey
said. If the threads are hanging on a lock somewhere in the host package
or Rx or something, this won't help a whole lot since we still have to
go through those layers and we'll still hang on those locks (same thing
for chewing up CPU, or moving memory around, etc). In fact, we'll do so
even more, since we (eventually) have to go through all that at least
twice for the VBUSY case.

But as I said, I don't think any of that is any reason to not _try_ if
you want to, since it's pretty easy to implement.

Andrew Deason