Re: does the linux NFS client support for failover to a replica share (read-only share)

[Malahal Naineni <malahal@us.ibm.com>]

J. Bruce Fields [bfields@fieldses.org] wrote:
> On Tue, Jun 07, 2016 at 10:02:19PM +0200, sebastien cabaniols wrote:
> > Hello linux-nfs mailing list.
> > 
> > I would like to know if the linux nfs client included in current
> > versions of the kernel supports fail-over to a replica on another nfs
> > server, I am using (manually) synchronized read-only shares...
> > 
> > I found very few information on Google about this topic and I suspect
> > this is not implemented.
> 
> That's correct (unless I've missed something!).
> 
> > I actually tried to setup this using SLES12SP1 (3.12.49 kernel) but I
> > failed so far. I am not attached to this distribution/version in
> > particular, just trying to see it working for real.
> > 
> > ( I did some "rpcdebug -m nfs" session and it seems the fs_locations
> > is not getting properly populated on my setup )
> > 
> > Any confirmation this should work or not would actually help me.
> > 
> > THX.
> > 
> > 
> > note from the exports man page:
> > 
> >        replicas=path@host[+host][:path@host[+host]]
> >               If  the  client  asks for alternative locations for the
> > export point, it will be given this list of alternatives.
> >               (Note that actual replication of the filesystem must be
> > handled elsewhere.)
> 
> Yes, the server side (assuming you've got the backend replication
> working) is pretty easy, and should work (though I don't know if it's
> gotten any testing).

Bruce, we did test the server side couple years ago. I don't remember
any issues on the server side. We did some rudimentary support on the
client side (we were using rsync for replication and our exports were
read-only!). I remember "find" having an issue with inode number change
while it was running, but don't remember any other issues. The client
patches never made it to mainline though.

Regards, Malahal.