Behind the panel
By Bob Hueston on Nov 15, 2007
A good question, and after digging through various documents to see what Sun says about the panel, I see exactly why the question is being asked. The only reference I could find to the panel was in the Sun SPARC Enterprise Server Family Architecture white paper, which says:
Mid-range and hign-end models of Sun SPARC Enterprise servers feature an operator panel to display server status, store server identification and user setting information, change between operator and maintenance modes, and turn on power supplies for all domains. [Emphasis added.]
The panel contains a small SEEPROM which an be accessed from the service processor (the XSCFU). OK, maybe no so small. I forget the exact size, but it's much larger than the 256 byte SEEPROM used for some FRU identification, and much, much smaller than a 73GB SAS disk. Let's split the difference logorithmically and assume it's in the range of a few dozen kilobytes.
In an ideal world, the panel SEEPROM would contain all of the non-volatile data stored on the XSCFU, so if the XSCFU fails and a new unit is installed, it can fully recover its state from the panel SEEPROM. Sadly, due to space limitations, that's simply not feasible. The XSCFU reserves in excess of 10MBs for error and fault logs alone, which could never fit in the SEEPROM.
Instead, the critical configuration data is stored in the panel SEEPROM. This includes hardware configuration (how XSBs are assigned to domains, network setup, etc), software settings (whether ssh is enabled, the email address for email notifications, etc.) and locally created user accounts and privileges. Pretty much the result of all 'set\*' commands ends up in the panel SEEPROM.
The things that are not stored in the panel SEEPROM include error and fault log files, and FRU information.
If the XSCFU fails and is replaced, the new XSCFU on power-on will recognize that it's installed in a new chassis. It will then go out and read the panel SEEPROM, and rebuild it's configuration data from the panel. It can then read the FRU ID SEEPROM from each FRU to rebuild its FRU inventory information. So the only real data that is lost is log files.