when i start the backup he moves always 4 blocks and stops. Last line says: wtf wrote 0 bytes, ret 2. Is this a known bug? I´ll try another SD card soon and update this post.
My second question: Is it possible to backup my Wii with another one´s NAND-backup? I´ve got the bootmii/boot2 installed.
YOu can only use a 'donor' nand after using betwiin to encrypt the other nand to use your own wii keys. Otherwise the wii cannot read it. Each wii uses different encryption / decryption keys for reading / writing to the nand. So no you cannot simply use another nand. It needs to be prepared first.