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Date:      Tue, 24 Apr 2018 08:14:32 +0200
From:      Karli =?ISO-8859-1?Q?Sj=F6berg?= <karli@inparadise.se>
To:        Rick Macklem <rmacklem@uoguelph.ca>, "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org>
Subject:   Re: pNFS server completed
Message-ID:  <1524550472.1130.10.camel@inparadise.se>
In-Reply-To: <YQBPR0101MB104218411EF6ABD1B660DEBDDD890@YQBPR0101MB1042.CANPRD01.PROD.OUTLOOK.COM>
References:  <YQBPR0101MB1042CB0BF460C68A908D9340DD8A0@YQBPR0101MB1042.CANPRD01.PROD.OUTLOOK.COM> ,<1524471526.9560.51.camel@inparadise.se> <YQBPR0101MB104218411EF6ABD1B660DEBDDD890@YQBPR0101MB1042.CANPRD01.PROD.OUTLOOK.COM>

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On Mon, 2018-04-23 at 21:00 +0000, Rick Macklem wrote:
> Karli Sj=C3=B6berg wrote:
> >=20
> > On Sun, 2018-04-22 at 21:18 +0000, Rick Macklem wrote:
> > >=20
> > > Hi,
> > >=20
> > > 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).
> > >=20
> > > If you are interested in more information or doing testing, see:
> > > http://people.freebsd.org/~rmacklem/pnfs-planb-setup.txt
> > >=20
> > > 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.
> > >=20
> > > If there are any volunteers on the doc side=C2=A0=C2=A0who would li=
ke to
> > > turn
> > > the above
> > > text file into a useful document, that would be greatly
> > > appreciated.
> > >=20
> > > Good luck with it, if you test it, rick
> > Hi Rick!
> >=20
> > I think this sounds amazing to have a distributed file server
> > natively
> > in FreeBSD, awesome!
> >=20
> > One question that comes to mind is about the MDS: wouldn=C2=B4t that =
be
> > a
> > SPOF?=C2=A0
> Yes, the MDS is just like a regular NFS server on FreeBSD. It is a
> single point
> of failure.
>=20
> >=20
> > Maybe that has already been discussed and explained and I=C2=B4ve jus=
t
> > 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).
>=20
> 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.
>=20
> 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.)
>=20
> 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



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