IPMI: snum vs id

Question

I'm using ipmiutils to look at a device and I see there is an ID column and an SNUM column. I've scanned the IPMI specification (it's huge -- just scanned) and the ipmiutils docs but can't find exactly what these mean.

Is one or the other stable, meaning (for example) that value 13 would always be the first fan in that particular chassis?

As far as I can tell, the values don't change, but I also don't have hot-swappable devices to plug in which could possibly alter what IPMI can report on.

Answer 1

Found my answers -- sharing for others.

ID is Record ID. According to the IPMI spec, section 33.1:

The Record ID field is used for record access. For example, a given instance of a sensor will always have the same Record Key information. The Record ID field, however can vary with time as records are added to and removed from the SDR Repository.

SNUM is sensor number. According to the IPMI spec, section 5.4:

The combination of Sensor Owner ID and Sensor Number uniquely identify a sensor in the system.

For SDR (sensor) records, the Record Key above is the Sensor Owner ID and Sensor Number according to section 43 "Sensor Data Record Formats".