In a previous post I mentioned some errors in the logs, those were regarding the harddrive of my firewall. It was dying.
After getting my hands on a couple of SATA DOM modules I was ready to do the transplant. This is almost rediculously easy!
First just save the config under Diagnostics > Backup/Restore.
I went with all and included the RRD data since I wanted the trafic history graphs.
Power off and switch the drive to the new.
Boot your installation media of choice and go ahead and install. I had an USB drive prepared since some earlier time ready for use.
Log in using the default username and password (admin/pfsense).
Then just go back to Diagnostics > Backup/Restore and upload and restore your config xml. The system will reboot and you are all done!
This is the point I realized that my graphs in fact did not work. Turns out the USB stick I had used had the i386 image on it, and my system was amd64 before this. Since I was already having the system down and had used an image with some time on it I tried the somewhat undocumented feature and used the system updater to change architecture. Under System > Firmware > Updater Settings I switched the URL to point to ADM64 and invoked the updater.
It worked like a charm! I have not been able to find any issues and my graphs are ok again.