From owner-freebsd-fs@FreeBSD.ORG Tue Dec 9 08:45:26 2014 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 4789972F for ; Tue, 9 Dec 2014 08:45:26 +0000 (UTC) Received: from kerio.tuxis.nl (alcyone.saas.tuxis.net [31.3.111.19]) (using TLSv1.1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id D3D4317B for ; Tue, 9 Dec 2014 08:45:24 +0000 (UTC) X-Footer: dHV4aXMubmw= Received: from [31.3.104.222] ([31.3.104.222]) by kerio.tuxis.nl (Kerio Connect 8.4.0); Tue, 9 Dec 2014 09:45:21 +0100 From: "Mark Schouten" Subject: Re: Mountd, why not use the '-S' flag by default To: "Rick Macklem" Organization: Tuxis Internet Engineering In-Reply-To: <891022143.8046492.1418095446417.JavaMail.root@uoguelph.ca> Message-ID: <20141209084521.05ccb5c7@kerio.tuxis.nl> Date: Tue, 09 Dec 2014 09:45:21 +0100 X-Mailer: Kerio Connect 8.4.0 WebMail X-User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2171.71 Safari/537.36 MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Cc: freebsd-fs@freebsd.org X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 09 Dec 2014 08:45:26 -0000 Hi, Rik Macklem wrote: > Well, there are a couple of things: > With "-S" all nfsd threads get suspended/resumed whenever exports > changes. This can result in a "pause" in NFS server response and > that might be considered a POLA violation. IMHO, An incidental raised latency is better than input/output errors wh= ich breaks files. > It only works for the new NFS server and not the old one and the > old one is still used by some. If it was the default, then the > old and new NFS servers would have had different behaviour. > (Again, this could be considered a POLA violation.) Backport=3F Or detect the old nfsd and ignore the -S flag if it is found= =3F > When "-S" was introduced by me, it was done as a "stop gap", since I > had thought that mountd would eventually be replaced by nfse > (and nfse did allow exports to be updated "atomically" so the problem > didn't occur). It now appears that no variant of nfse will end up > in FreeBSD. That's more of a reason to enable it by default, if you ask me. > The last one is noted in the description. If, for some reason, mountd > crashes during a reload, then all the nfsd threads could be stuck > suspended. (I don't know if this occurs in practice.) I've tested (not thoroughly) and I didn't get my client to break. Even w= ith errors in the exports-file, stuff kept working. Doesn't most of NFS = break without mountd anyways=3F > Basically, I am a coward w.r.t. POLA and almost never change a > default. (The one case I did change was making rsize, wsize > default to MAX=5FBSIZE instead of 32K. By some strange twist of > fate, this caused a lot of grief, since there was a bug related > to TSO segments just under 64K for network interfaces that are > limited to 32 transmit segments. I am still saying "disable TSO" > to people running older FreeBSD systems because of this.;-) Hehe. :) All I can say is that I would prefer rsize and wsize to be bigg= er. But that's a different story. :) Regards, -- Kerio Operator in de Cloud=3F https://www.kerioindecloud.nl/ Mark Schouten | Tuxis Internet Engineering KvK:=C2=A061527076=C2=A0| http://www.tuxis.nl/ T: 0318 200208 | info@tuxis.nl