Re: Is NFS v4 stable and recommend to use now?

["J. Bruce Fields" <bfields@fieldses.org>]

On Sat, Oct 04, 2008 at 09:34:49PM +0800, Roy M. wrote:
> Hello,
> 
> On Sat, Oct 4, 2008 at 5:52 AM, J. Bruce Fields <bfields@fieldses.org> wrote:
> > I doubt the pattern of I/O really matters much--it's the opens and
> > closes themselves that matter.
> >
> > (In v3, close-to-open cache consistency requires that the client always
> > fetch file attributes from the server on an open.  That means open() is
> > always going to take at least the ping time to the server.  In v4 in
> > some situations the client can do the open with no call to the server at
> > all--by comparison such an open is almost instantaneous.  If you're
> > doing a ton of opens all in a row, that may make a difference.)
> >
> 
> In existing v3, you mean even if a file is cached locally by client,
> in each open, the file attributes need to be read from NFS server
> everytime?

Right.  The client has to do that to check whether someone else has
changed the file.  See http://nfs.sourceforge.net/#faq_a8 for an
explanation of close-to-open cache consistency, which is what requires
this.

> But I just wonder without reading the NFS server, how the consistency
> was maintained...

I'm afraid I don't understand the question.

--b.