pNFS server completed

[Karli Sjöberg]

On Mon, 2018-04-23 at 21:00 +0000, Rick Macklem wrote:
> Karli Sjöberg wrote:
> > 
> > On Sun, 2018-04-22 at 21:18 +0000, Rick Macklem wrote:
> > > 
> > > Hi,
> > > 
> > > I have now updated the projects/pnfs-planb-server subtree of svn
> > > with
> > > what
> > > I believe is a complete pNFS server. It now handles mirrored Data
> > > Servers (DSs)
> > > and recovery of a failed mirrored DS while the service is
> > > operational.
> > > It handle non-pNFS clients (such as NFSv3 mounts) via having the
> > > MetaData
> > > Server act as a proxy for Read/Write operations.
> > > For pNFS capable NFSv4.1 clients, the Read/Write operations are
> > > done
> > > directly
> > > on the appropriate DS(s), avoiding the MetaData Server (which act
> > > like a normal
> > > NFS server except for pNFS capable clients).
> > > 
> > > If you are interested in more information or doing testing, see:
> > > http://people.freebsd.org/~rmacklem/pnfs-planb-setup.txt
> > > 
> > > I hope that this should be ready for head/current with some
> > > additional testing.
> > > I will post here asking the "collective" about this when I think
> > > it
> > > is ready.
> > > 
> > > If there are any volunteers on the doc side  who would like to
> > > turn
> > > the above
> > > text file into a useful document, that would be greatly
> > > appreciated.
> > > 
> > > Good luck with it, if you test it, rick
> > Hi Rick!
> > 
> > I think this sounds amazing to have a distributed file server
> > natively
> > in FreeBSD, awesome!
> > 
> > One question that comes to mind is about the MDS: wouldn´t that be
> > a
> > SPOF? 
> Yes, the MDS is just like a regular NFS server on FreeBSD. It is a
> single point
> of failure.
> 
> > 
> > Maybe that has already been discussed and explained and I´ve just
> > missed it, but would be nice to know. And if it is a SPOF, are
> > there
> > any plans of also mirroring MDS's as well? Perhaps a DS can be MDS
> > to,
> > something like that?
> No plans w.r.t. mirroring the MDS. The pNFS client using Flexible
> File Layout
> knows to write to both mirrors (and the MDS can do so acting as a
> proxy
> for a client).
> 
> However, NFS clients don't know how to do NFS operations on multiple
> NFS servers. As such, any mirroring would have to be implemented
> "behind the
> curtain" and I'll admit I don't know how to do that.
> 
> I did try using a clustered file system (GlusterFS) as a backend when
> I first
> implemented a pNFS server two years ago, but that was a failure, due
> to
> terrible performance. (Using a clustered file system as a storage
> backend would
> make multiple NFS servers/MDSs more feasible, but it didn't work.)
> 
> rick

OK, I think I understand, thank you for the explanation!

So you could say that this enhancement is more about the performance
benifit of scaling out, rather than resiliance/tolerance?

/K