Slow NFS writes with sec=krb5

[Florian Oppermann]

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Sorry for talking to myself…

> 1) On one slow machine that is running precise I booted into an
> old kernel image (3.2 instead of 3.13). The behaviour was the
> expected: The kerberized automount got fast write speeds. Booting
> back to 3.13 made it slow again.

I expanded this test scenario on one of our trusty machines and
installed some old kernel versions: From 3.2 to 3.11.10.15 the NFS
mount was fast, it got slow at version 3.12.0rc1 (last two packages
for saucy). (Note: I refer to the packages from
<http://kernel.ubuntu.com/~kernel-ppa/mainline/>.)

Maybe someone with more knowledge about NFS or kernel development
could have a look at the changelog
(<http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.12-rc1-saucy/CHANGES>
).
I believe some change there has undesired effects in certain environment
s.

Best regards,
Florian

On 05.10.2015 18:14, Florian Oppermann wrote:
> On 05.10.2015 17:25, Brandon Vincent wrote:
>> There was an issue with the system detecting if gssd was
>> running, so my only recommendation to you is to update to the
>> latest kernel and NFS/Kerberos related packages and see if that
>> resolves your issue.
> 
> I just tried the following things:
> 
> 1) On one slow machine that is running precise I booted into an
> old kernel image (3.2 instead of 3.13). The behaviour was the
> expected: The kerberized automount got fast write speeds. Booting
> back to 3.13 made it slow again.
> 
> I think this rules out the possibility that some other packages
> have broken something and should be upgraded.
> 
> 2) On one of our trusty machines I installed the .debs for 4.0.0, 
> 4.1.0, 4.2.3 and 4.3.0 from 
> <http://kernel.ubuntu.com/~kernel-ppa/mainline/>. None of the new 
> kernels enabled the fast kerberized NFS automount.
> 
> I suspected them to solve the issue because my laptop with Debian 
> testing had fine write performance. I have to check the kernel
> version though.
> 
> Maybe we’ll just try to setup one machine with a clean 15.10 when
> it’s released.
> 
> Best regards, Florian
> 
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