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

[Linus van Geuns <linus@xxxxxxxxxxxxx>]

On Fri, Feb 11, 2011 at 3:39 AM, Fajar A. Nugraha <list@xxxxxxxxx> wrote:
[..]
> I'm pretty sure you can choose round robin in Linux. From iputils'
> README.bonding:
> mode
>         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
>                 tolerance.

If you switch "mode" to LACP (802.3ad), bonding uses a hash algorithm
to decide which slave to transmit any frame over.

Documentation/networking/bonding.txt.gz:
[..]
mode

        Specifies one of the bonding policies. The default is
        balance-rr (round robin).  Possible values are:
[..]
        802.3ad or 4

                IEEE 802.3ad Dynamic link aggregation.  Creates
                aggregation groups that share the same speed and
                duplex settings.  Utilizes all slaves in the active
                aggregator according to the 802.3ad specification.

                Slave selection for outgoing traffic is done according
                to the transmit hash policy, which may be changed from
                the default simple XOR policy via the xmit_hash_policy
                option, documented below.  Note that not all transmit
                policies may be 802.3ad compliant, particularly in
                regards to the packet mis-ordering requirements of
                section 43.2.4 of the 802.3ad standard.  Differing
                peer implementations will have varying tolerances for
                noncompliance.
[..]

>>
>> 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.

Sure. You could, for instance, create a bond using two interfaces,
each connected to a different switch, and use "active-backup" to avoid
losing storage connectivity if one switch fails (resulting in loss of
link).

If you want to use some load balancing not recognized by any network
equipment in your flow path, you should test for possible side effects
first.

Regards, Linus

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