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Re: [Xen-users] bonding with trunking AND iscsi

  • To: Xen User-List <xen-users@xxxxxxxxxxxxxxxxxxx>
  • From: "Fajar A. Nugraha" <list@xxxxxxxxx>
  • Date: Fri, 11 Feb 2011 09:39:39 +0700
  • Delivery-date: Thu, 10 Feb 2011 18:40:26 -0800
  • List-id: Xen user discussion <xen-users.lists.xensource.com>

On Fri, Feb 11, 2011 at 6:16 AM, Linus van Geuns <linus@xxxxxxxxxxxxx> wrote:
Hey Donny,

as Jeff already stated, you can bond multiple NICs connected to the
same switch to a single trunk/logical link and put VLAN interfaces on
top of that (with some hacks - see the kernel doc on bonding).
The LACP link aggregation might not scale the bandwidth as you expect it to.
For each packet, the bonding code decides which slave (NIC) to use for
output using a hash calculated from layer2(MAC), layer2+3(MAC+IP) or
layer3+4(IP+ports). This means a single packet flow (eg I/O traffic
with a single iSCSI target) from one host to another will never use
more than one NIC (bandwidth).
In fact, as there is no dynamic load balancing or round robin, you
might even share one NIC for multiple iSCSI packet flows and have the
other slaves (NICs) idle.

I'm pretty sure you can choose round robin in Linux. From iputils' README.bonding: 


        Specifies one of the bonding policies. The default is
        balance-rr (round robin).  Possible values are:

        balance-rr or 0

                Round-robin policy: Transmit packets in sequential
                order from the first available slave through the
                last.  This mode provides load balancing and fault

This is why I dropped the VLAN over LACP trunk idea. ;-)

IMHO VLAN over bonding is a good idea. Just make sure you manage the setup using OS' configuration (/etc/sysconfig/network-scripts/ifcfg-* on RH), and NOT rely on xend's default network-bridge script.


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