to prevend the sdcard to fail,
Not "prevent" but "significantly slow down". As macom explained above how folder2ram works: "...when the SBC is shut down the RAM is synced to the SD card..." So there is writing to the SD card, but it is greatly reduced by way of the Flash Memory plug-in. Nothing lasts forever, but with the Flash Memory plug-in your SD card will last much longer. Having a working back-up of that system SD card is a must, unless you enjoy starting over from scratch some day in the future. I have had several SD cards running for a couple of years now. But as I said, nothing lasts forever.