It would be great to have some semi-permanent memory on board RasPi. Either NOVA-RAM, or FRAM.
Why ?
Many RasPi is used for data collection.
New large SD-cards do not take but about 2000 R/W cycles.
Using SD card for data collection destroys the card in a year or even some months.
Collecting data solely to TMPFS on RAM does not work, if there is possibility for electricity dropdowns.
Thats why I collect to RAM 24h and append the data to SD by midnight. This way only one day gets lost of the data.
The best way would be to collect the data to a semi-permanen memory and move it to SD when the memory gets full.
An IIC FRAM FM24CL26 is so small 8 pin chip that it should find space on RaspberriPi board.