Received-SPF: pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210921143259.GB21704@fieldses.org> <37851433-48C9-4585-9B68-834474AA6E06@oracle.com>
 <20210921160030.GC21704@fieldses.org>
In-Reply-To: <20210921160030.GC21704@fieldses.org>
From:   Daire Byrne <daire@dneg.com>
Date:   Wed, 22 Sep 2021 10:47:35 +0100
Message-ID: <CAPt2mGOf8orCkOj9hCM_sSu2uucPiRFPEK+yep+kufv-cDvhSA@mail.gmail.com>
Subject: Re: [PATCH] nfs: reexport documentation
To:     Bruce Fields <bfields@fieldses.org>
Cc:     Chuck Lever III <chuck.lever@oracle.com>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Tue, 21 Sept 2021 at 17:00, Bruce Fields <bfields@fieldses.org> wrote:
>
> > Any recommended workarounds? Or does this simply mean that
> > administrators need to notify client users to unmount (or
> > at least stop their workloads) before rebooting the proxy?
>
> I think so.
>
> If you don't use any file locking or delegations I suppose you're also
> OK.  Delegations might be useful, though.
>
> I'd expect reexport to be useful mainly for data that changes very
> rarely, if that helps.
>
> --b.

Firstly, it's great to see this documentation and the well maintained
wiki page for something we use in production (a lot) - thanks Bruce!

I can only draw on our experience to say:
* if the nfs re-export server doesn't crash, we rarely have cause to reboot it.
* we re-export read-only software repositories to WAN/cloud instances
(an ideal use case).
* we also re-export read/write production storage but every client
process is writing unique files - there are no writes to the same
file(s) from any clients of the re-export server.

We don't use or need crossmnt functionality, but I know from chatting
to others within our industry that the fsid/crossmnt limitation causes
them the most grief and confusion. I think in the case of Netapps,
there are similar problems with trying to re-export a namespace made
up of different volumes?

As noted on the wiki, the only way around that is probably to have a
"proxy" mode (similar to what ganesha does?).

Daire