counterfeit SD cards are still an issue checking with F3 / H2testw directly after purchase is highly recommended. - How to prepare a SD card? / SDCard list

Speed Class

F3 - F ight F lash F raud

• github

## WARNING - This will destroy any previously stored data on your disk!
# ./f3probe --destructive --time-ops /dev/sdb

In case you chose an SD card that was already in use before please consider resetting it back to ‘factory default’ performance with SD Formatter before burning (explanation in the forum).

Write the xz compressed image with USBImager or balenaEtcher on all platforms since unlike other tools, either can validate burning results saving you from corrupted SD card contents.

Also important: Most SD cards are only optimised for sequential reads/writes as it is common with digital cameras. This is what the speed class is about. The SD Association defined Application Performance Class as a standard for random IO performance.

Backup

$ cat /dev/sdb > sdcard.dump	# use progress -w to see avancement