How do you setup your pool? Your parity drive shouldn't be in the pool. Look at the picture section 9 or read the second passage.
You have to distinguish data (Daten) from content (Inhalt). Content only meens the checksum file snapraid creates to check or restore data, if I'm not wrong. On the picture from technikaffe there is only content marked for the parity drive and therefor no data (your files) will be stored at this drive.