@rickkas7, I've been using SdFat on an Electron (SPI) very successfully (thanks!). However, my code is designed to store files on the SD and then go to sleep using
System.sleep(uint16_t wakeUpPin, uint16_t edgeTriggerMode, long seconds,SLEEP_NETWORK_STANDBY);
Since this uses an STM32 STOP, the code continues from where it left off after the call and RAM should be maintained. However, the SD does not work. Note that I do turn off power to the SD (via FET) before sleeping and then back on (with delay to allow it to start up). However, not sure that shouldn't affect anything.
My question is, what's the best approach for maintaining SD functionality through the sleep?