Multiple BMCs in a system: IPMB? Redfish? MCTP?

[Deepak Kodihalli]

On 30/04/20 4:21 am, Nancy Yuen wrote:
> I've talked with some people a while back (long while back) about 
> multiple BMCs in a system.  Either for redundancy or managing separate 
> parts of a system.   I'm wondering what other people are thinking in 
> this area if at all.
> 
> We are considering similar designs and I'm looking into options for 
> BMC-BMC communications.  Some BMCs may not be externally 
> accessible. Here are some options that we've looked at:
> 
>  1. i2c/IPMB
>  2. usbnet/Redfish
>  3. i2c/MCTP/PLDM or something else?
>  4. internal network via switch chip/Redfish or MCTP
> 
>   I'd like to reduce our use of IPMI so I want to avoid (1).
> 
> ----------
> Nancy

Hi Nancy,

I think it depends on whether the BMCs need to talk to each other for 
platform management, or if they manage their own hosts and we need one 
of the BMCs to broadcast out of band requests and aggregate responses.

For the former I think PLDM over MCTP could be a good fit. This is more 
of an "inband" use-case in my opinion so I'm not sure if Redfish is well 
suited. For the latter, a Redfish based aggregation is a good option.

Regards,
Deepak