Date: Tue, 09 Dec 2014 09:45:21 +0100 From: "Mark Schouten" <mark@tuxis.nl> To: "Rick Macklem" <rmacklem@uoguelph.ca> Cc: freebsd-fs@freebsd.org Subject: Re: Mountd, why not use the '-S' flag by default Message-ID: <20141209084521.05ccb5c7@kerio.tuxis.nl> In-Reply-To: <891022143.8046492.1418095446417.JavaMail.root@uoguelph.ca>
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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
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