I am using the same simple logging code that you have posted with just the raw read and write. The initialization seems to go fine, and then it acts like it is reading and writing even when i have the SD card removed from the slot. I enter the 'r' command, and it prints the same info, not zeros or junk. when i reset, it loses the info. It is as if it is just storing it in on board memory until it resets, like it isn't even using the sd card at all, and then loses the data when it resets.
Thank you Agent Orange for working on this project.