I bought a new 32GB micro-cd card.
So I put it into my nano with the newest firmware, and tried to format it using the Web-UI.
It just did not work. So I dd-ed the first 1M with zeros, rebooted the Nano, and it worked, as I could see on the UI:
/dev/sdcard/sd1 28.1G 44.4M 26.7G 0% /sd
Actually I cannot go back to that state to check the difference, and I did not make any notes.
All I could see was 2 partitions, and it was on /dev/sda1 and /dev/sda2