Return-Path: linux-nfs-owner@vger.kernel.org Received: from smtp6-g21.free.fr ([212.27.42.6]:52955 "EHLO smtp6-g21.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754052Ab3IKPL4 convert rfc822-to-8bit (ORCPT ); Wed, 11 Sep 2013 11:11:56 -0400 Date: Wed, 11 Sep 2013 17:11:45 +0200 From: Emmanuel Florac To: Emmanuel Florac Cc: linux-nfs@vger.kernel.org Subject: Re: Hard to debug NFS loss of connectivity: problem solved Message-ID: <20130911171145.323f9b9e@harpe.intellique.com> In-Reply-To: <20130905191800.1c75b2fb@harpe.intellique.com> References: <20130905191800.1c75b2fb@harpe.intellique.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-nfs-owner@vger.kernel.org List-ID: Le Thu, 5 Sep 2013 19:18:00 +0200 Emmanuel Florac ?crivait: > Any hint, idea, etc would be extremely welcome. Even some > debugging method less painful than digging through huge > tcpdumps would be nice :) I post this answer in the faint hope that it may avoid a long and painful week of testing to someone else :) The problem comes from the virtual network adapter "Intel pro 1000" using the e1000e linux driver. The Intel hardware supports a MTU of 4078 max. On a physical machine, it will fail to set up a greater value with something like: # ifconfig eth0 mtu 4079 SIOCSIFMTU: Invalid argument However the virtual e1000 from VMWare ESX silently accept any value; then it will mostly work, and fail in mysterious way and only with certain protocols (such as nfs). In the case of VMWare virtual machines, using a vmnet3 virtual network adapter works fine with a mtu of 9000 under NFS. Therefore the problem is solved. For the sake of completeness and curiosity, I'll try and see what happens with a KVM e1000 virtual device. -- ------------------------------------------------------------------------ Emmanuel Florac | Direction technique | Intellique | | +33 1 78 94 84 02 ------------------------------------------------------------------------