Re: Hard to debug NFS loss of connectivity: problem solved

["J. Bruce Fields" <bfields@fieldses.org>]

On Wed, Sep 11, 2013 at 05:11:45PM +0200, Emmanuel Florac wrote:
> Le Thu, 5 Sep 2013 19:18:00 +0200
> Emmanuel Florac <eflorac@intellique.com> écrivait:
> 
> > 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).

Ah-hah!

Thanks for the followup.--b.

> 
> 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
>                     |	<eflorac@intellique.com>
>                     |   +33 1 78 94 84 02
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