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Re: [lvs-users] LVS-DR Director not passing some packets

To: "'LinuxVirtualServer.org users mailing list.'" <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [lvs-users] LVS-DR Director not passing some packets
From: "Dave Whitehouse" <dave@xxxxxxxxxx>
Date: Fri, 21 Mar 2008 17:58:38 -0000
We have found some other issues that could have been causing the real
servers to fail the health check intermittently. This obviously wouldn't
help matter.

However the packet trace did appear to point to the director not forwarding
to the real server.

I have setup a similar config in a test lab and have got 33000 InPPS  with
no problems so I'm thinking it is not LVS related at the moment.

Thanks for the input thou' guys and I'll keep you posted.

-----Original Message-----
From: lvs-users-bounces@xxxxxxxxxxxxxxxxxxxxxx
[mailto:lvs-users-bounces@xxxxxxxxxxxxxxxxxxxxxx] On Behalf Of Graeme Fowler
Sent: 11 March 2008 10:00
To: LinuxVirtualServer.org users mailing list.
Subject: Re: [lvs-users] LVS-DR Director not passing some packets

Hi

Just to add to Joe's comments...

On Mon, 2008-03-10 at 10:39 +0000, Dave Whitehouse wrote:
> Just looking for some advice around problem solving my LVS cluster
> performance.
> 
> I have a cluster that currently has two LVS Directors hosting 4 VIPS. I
use
> keepalived 1.1.13 on the directors, running on CentOS 4.4. Real servers
are
> all CentOS 4.4 too.

CentOS 4 is a bit behind the bleeding edge but that does give it the
benefit of being somewhat more stable than, for example, Fedora :)

> I have hit an issue where my directors appear to be dropping packets. My
> connection rate is low when this occurs, typically about 40+ InPPS which
is
> very low :-(

That is fairly low.

> A packet trace appears to indicate that packets are hitting the director
but
> not coming out again.

As in, not being forwarded to the realservers?

> I have iptables running on the directors and ip_contrack is loaded along
> with a few other iptable related kernel modules. My question is do you
thing
> that iptables could be causing problems with my LVS and if so have you any
> suggestions where and how I could prove it ?

Well, the easiest thing to do is to remove all the iptables rules and
unload the modules, then test. If the same problem occurs, you've found
that it isn't iptables and conversely if it doesn't, then it is.

You can then build your ruleset back up bit by bit and see which part
causes the problem.

For us to help you further we probably need to see your keepalived
config, the output from ipvsadm in normal operation and the output from
ipvsadm when there's a problem.

Also, have you "cloaked" the realservers to prevent them repsonding to
ARP requests for the VIP?

Graeme



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