[Linux-cluster] Bonding Interfaces: Active Load Balancing & LACP

[Radu Rendec]

I also experimented with D-Link DGS-3xxx switches and the bonding
driver, but in a quite strange configuration: 2 distinct switches
without any "knowledge" of each other, and with each server having NIC
#1 connected in one switch and NIC #2 in the other.

In my case, the bonding driver actually splitted the traffic between the
2 links and I could achieve higher speeds than with a single link. This
is my config (nothing fancy):

[root at host ~]# cat /etc/sysconfig/network-scripts/ifcfg-bond2 
DEVICE=bond2
TYPE=Bonding
BONDING_OPTS="miimon=50"
ONBOOT=yes
BOOTPROTO=none
BRIDGE=br2

The bond interface was assigned to a bridge in my case, because I needed
to give network access to some VMs (besides the physical host).

If you don't need 802.1q tagging, I think you could try to create 2
VLANs in your switch and for all servers have one NIC in one vlan and
and another NIC in the other vlan and then a bond across those 2 NICs.

The drawback is that everything that is connected in this manner needs
to have exactly 2 NICs connected in the 2 VLANs. The other problem is
that if one NIC fails in one of the servers, it won't receive the
packets that are sent on the corresponding VLAN, so the server will not
receive half of the traffic that is meant for it.

I'm also curious about the results of your experiments. Please post back
if you have time.

Thanks,

Radu Rendec

On Thu, 2012-06-07 at 00:35 -0400, Digimer wrote:
> I know that the only *supported* bond is Active/Passive (mode=1), which 
> of course provides no performance benefit.
> 
> I tested all types, using more modest D-Link DGS-3100 switches and all 
> other modes failed at some point in failure and recovery testing. If you 
> want to experiment, I'd suggest tweaking corosync's timeouts to be 
> (much?) more generous.
> 
> I'm curious to hear back on what your experimenting finds.
> 
> Digimer
> 
> On 06/07/2012 12:12 AM, Eric wrote:
> > I'm currently using the HP Procurve 2824 24-port Gigabit Ethernet switch
> > to for a backside network for synchronizing file systems between the
> > nodes in the group. Each host has 4 Gigabit NIC's and the goal is to
> > bond two of the Gigabit NIC's together to create a 2 Gbps link from any
> > host to any other host but what I'm finding is that the bonded links are
> > only capable of 1 Gbps from any host to any other host. Is it possible
> > to create a multi-Gigabit link between two hosts (without having to
> > upgrade to 10G) using a switch that "uses the SA/DA (Source
> > Address/Destination Address) method of distributing traffic across the
> > trunked links"?
> >
> > The problem, at least as far as I can tell, comes down to the limitation
> > of ARP resolution (in the host) and mac-address tables (in the switch):
> >
> > When configured to use Active Load Balancing, the kernel driver leaves
> > each of the interface's MAC addresses unchanged. In this scenario, when
> > Host A sends sends traffic to host Host B, the kernel uses the MAC
> > address of only one of Host B's NIC's as the DA. When the packet arrives
> > at the switch, the switch consults the mac-address table for the DA and
> > then sends the packet to the interface connected to the NIC with MAC
> > address equal to DA. Thus packets from Host A to Host B will only leave
> > the switch through one interface - the interface connected to the NIC
> > with MAC address equal to DA. This has the effect of limiting the
> > throughput from Host A to Host B to the speed of the one interface
> > connected to the NIC with MAC address equal to DA.
> >
> > When configured to use IEEE 802.3ad (LACP), the kernel driver assigns
> > the same MAC address to all of the hosts' interfaces. In this scenario,
> > when Host A sends traffic to Host B, the kernel uses Host B's shared MAC
> > address as the DA. When the packet arrives at the switch, the switch
> > creates a hash based on the SA/DA pair, consults the mac-address table
> > for the DA, and and assigns the flow (i.e., traffic from Host A to Host
> > B) to one of the interfaces connected to Host B. Thus packets from Host
> > A to Host B will only leave the switch through one interface - the
> > interface determined by the SA/DA hash. This has the effect of limiting
> > the throughput from Host A to Host B to the speed of the one interface
> > determined by the hashing method. However, if the flow (from Host A to
> > Host B's shared MAC address) were to be distributed across the different
> > interfaces in a round-robin fashion (as the packets were leaving the
> > switch) the throughput between the hosts would equal the aggregate of
> > the links (IIUC).
> >
> > Is this a limitation of the the Procurve's implementation of LACP? Do
> > other switches use different methods of distributing traffic across the
> > trunked links? Is there another method of aggregating the links between
> > the two hosts (e.g., multipathing)?
> >
> > TIA,
> > Eric Pretorious
> > Truckee, CA
> >
> >
> > --
> > Linux-cluster mailing list
> > Linux-cluster at redhat.com
> > https://www.redhat.com/mailman/listinfo/linux-cluster
> 
>