Re: Fault tolerant NAS

[Chuck Yerkes <chuck+obsd_(_at_)_2004_(_dot_)_snew_(_dot_)_com>]

Quoting Matt Provost (mprovost_(_at_)_termcap_(_dot_)_net):
> On Apr 20 09:09 AM, Balazs Nagy wrote:
> > Hi there,
> > 
> > Has anyone used OpenBSD to create a fault tolerant NAS?
> > 
> > It seems that carp could handle the front end, but how
> > to replicate between two SCSI or Fiber systems?  I'm
> > thinking of a hardware architecture like here:
> > http://www.winsys.com/products/flnas_confi_nspfserv.php
> > 
> > Cheers,
> > 	Bal?zs
> > 
> > http://www.thenewpush.com
> 
> I assume you're talking about NFS in this example. Although carp can
> move the IPs around, I think you'll find that an NFS server isn't quite
> as stateless as you'd like. Any failover NFS implementation that I've
> seen requires some syncing of filehandles between the servers, at least.
> You'd have to have something like pfsync for NFS before the clients
> would fail over without noticing. I think if you'd try it now you'd just
> get a lot of stale file handle messages after a failover.

Actually (at least for NFSv2) it *is* stateless.

And if you can toss a RAID array (or disk) from one server to
another (a non-trivial matter to arrange well), and you present
the same MAC/IP address to the network, clients won't notice a
failover.