[Lustre-discuss] Lustre behaviour when multiple network paths are available?

[Andreas Dilger]

On Feb 07, 2008  15:05 -0800, Klaus Steden wrote:
> When Lustre is configured in an environment where there are multiple paths
> to the same destination of the same length (i.e. two paths, each one hop
> away), which path(s) will be used for sending and receiving data?

That depends on how you configure it in /etc/modprobe.conf.

> I have my cluster configured with two OSTs with two GigE NICs in each. I am
> seeing identical performance metrics when I use LACP to aggregate, and when
> I use two separate network addresses to connect them (ditto on the client
> side).
> 
> So what I'm wondering is if I've hit the peak performance of my disk array,
> or if Lustre is just using only one path. The numbers I'm seeing in both
> scenarios indicate 95% utilization of GigE, times two.

I'm not sure I understand - if you are getting aggregate performance that
is 190% of a single GigE from the client then you _have_ to be using both
paths (assuming there are two GigE NICs in the client, and not four).

> How can I get Lustre to use both paths simultaneously?

ifconfig should show you clearly via TX/RX byte counts which NICs are
being used in each configuration.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.