Cannot access files on 1TB MBL

WD Legacy Products My Book Live
35

Well that yielded an interesting result:

MyBookLive:~# mount -o noatime,nodiratime /dev/sda4 /DataVolume
mount: /dev/sda4 already mounted or /DataVolume busy
mount: according to mtab, /dev/sda4 is already mounted on /DataVolume