Re: Slow NFS Performance

roger
Mon, 31 Mar 2008 20:48:27 -0000

On Mon, 2008-03-31 at 20:18 +0100, Andrew Suffield wrote:

> My bet is on a kernel, hardware, or network fabric issue that was
> shaken loose by the brief traffic interruption that occurs when
> shorewall starts. It could also be a traffic shaping corner case (some
> flawed configurations have cascade failure modes, where everything
> seizes up for certain traffic patterns but not others, and the effect
> is self-continuing).

>
> Other significant data points:
>
>  - what''s on the network when the problem occurs? Steady-but-slow
NFS
>  traffic, fast-but-rare bursts, collisions, corrupted packets,
>  something else entirely? Whenever I see something like this, I hit
>  tcpdump -w first and think about it later; a packet dump explains
>  most issues when you can study it at leisure.
>
>  - relevant /proc/mounts entries. Do these change when the problem occurs?
>
>  - physical network configuration
>
>  - vmstat output when the problem occurs
>
> But I doubt it''s a shorewall problem.

Right, it is possible the laptop''s kernel hibernation
(Suspend2/TuxOnIce) process is faulty on resume.

A more likely scenario I just thought of, switching between a wireless
(wlan0) and wired NIC (eth0), even though I''m keeping the same IP
address for both NICs, the kernel netfilter might get confused?

--
Roger
http://www.eskimo.com/~roger/index.html
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Mon Mar 31 12:48:25 AKDT 2008