I was working on an embedded system that had a primary board and a backup board. I wrote the code that kept the data on the backup board in sync. And you coul

I was working on an embedded system that had a primary board and a backup board. I wrote the code that kept the data on the backup board in sync. And you could update the software on the backup board, reboot it, wait for the data to re-sync, swap which board was primary, then update the software on the former (now backup) board and reboot it. This let you update the system without it ever going down, and without losing any data. The little extra was that the code for all this was in a file named Redun.C.