[ewg] IPoIB to Ethernet routing performance

[Jabe]

On 12/26/2010 11:57 AM, Richard Croucher wrote:
> The vNIC driver only works when you have Ethernet/InfiniBand hardware
> gateways in your environment.   It is useful when you have external hosts to
> communicate with which do not have direct InfiniBand connectivity.
> IPoIB is still heavily used in these environments to provide TCP/IP
> connectivity within the InfiniBand fabric.
> The primary Use Case for vNICs is probably for virtualization servers, so
> that individual Guests can be presented with a virtual Ethernet NIC and do
> not lead to load any InfiniBand drivers.  Only the hypervisor needs to have
> the InfiniBand software stack loaded.
> I've also applied vNICs in the Financial Services arena, for connectivity to
> external TCP/IP services but there the IPoIB gateway function is arguably
> more useful.
>
> The whole vNIC arena is complicated by different, incompatible
> implementations from each of Qlogic and Mellanox.
>
> Richard
>    


Richard, with your explanation I understand why vNIC / EoIB is used in 
the case you cite, but I don't understand why it is NOT used in the 
other cases (like Ali says).

I can *guess* it's probably because with a virtual ethernet fabric you 
have to do all IP stack in software, probably without even having the 
stateless offloads (so it would be a performance reason). Is that the 
reason?

Thank you