another way: keep /storage on the SD, mount the hdd normal (e.g. as /var/media/storage2), delete the data directories (tvshows, videos, etc.) and make softlinks to the directories on your hdd under /storage
tvshows -> /var/media/storage2/tvshows
videos -> /var/media/storage2/videos
etc...
Only when you upload files over samba the hdd is written. If you still get corruption on the hdd, there is something wrong with your hardware.