The problem seems to be fixed for me.
With the latest kernel-update I noticed that my drive is mapped to /dev/hda again (instead of sda). So I removed the workaround (which would not effect the drive anyway since it doesnt show up /sys/class/scsi_disk/ anymore) and the hdd still shuts down properly.
The problem seems to be fixed for me. scsi_disk/ anymore) and the hdd still shuts down properly.
With the latest kernel-update I noticed that my drive is mapped to /dev/hda again (instead of sda). So I removed the workaround (which would not effect the drive anyway since it doesnt show up /sys/class/