[ovs-discuss] Bonding problems with redundant physical switching

[Jesse Gross]

On Wed, Sep 15, 2010 at 4:47 PM, Ben Pfaff <blp at nicira.com> wrote:
> On Wed, Sep 15, 2010 at 04:39:50PM +0000, Jesse Gross wrote:
>> On Wed, Sep 15, 2010 at 4:29 PM, Ben Pfaff <blp at nicira.com> wrote:
>> > On Wed, Sep 15, 2010 at 12:17 AM, Christian Fischer
>> > <christian.fischer at easterngraphics.com> wrote:
>> >> You sad that I can use OVS with Linux bonding, how is that to do?
>> >> Simply loading the bonding kernel module causes segmentation fault, in my
>> >> case. Can/Must I compile OVS with linux bonding support?
>> >
>> > Hmm, it looks like the bonding module depends on the bridge module, at least
>> > on some Linux kernel versions.  Indeed, it may not be possible to use the
>> > Linux bonding at the same time as Open vSwitch for Linux before 2.6.36.
>>
>> Actually Linux bonding should not be used with Open vSwitch even if it
>> were not for this interaction with the bridge module.  Bonding has a
>> number of interesting interactions with the learning table and Open
>> vSwitch has code to handle this but only if the bonding is handled by
>> OVS itself.  As a result, Linux bonding may work (assuming a new
>> enough kernel version), however, you are likely to run into a number
>> of difficult to diagnose corner cases.
>
> I was under the impression that those corner cases were problems
> specific to the type of bonding that OVS already implements; that is,
> bonding where the first-hop switch was unaware of and not participating
> in the bond.  Doesn't LACP, etc. avoid that kind of problem, acting much
> more like a single link than SLB does?

Yes, LACP should be much more resilient to these types of issues.
However, I don't think that LACP will help in this particular
situation since the physical switches are cheap and not stacked.
Linux supports a half dozen different types of bonding though (at
least some which probably have issues with OVS) and apparently they
don't work together at all on any released kernel version, so I
wouldn't say that it is either supported or encouraged.