[IriDium]

False alarm.

Dumb alert. I was running the command on a partition, not the whole disk. All works well in Ubuntu.

Terminal

sudo hdparm -I /dev/sdd|grep -i trim

showed that trim was supported.
so

Terminal

sudo fstrim -v /media/

worked

Terminal

sudo fstrim -v /media/SSD-Data

failed

However, under Xbian, the mount points are different and I get the error

Terminal

xbian@DogStar ~ $ sudo fstrim -v /
fstrim: /: FITRIM ioctl failed: Operation not supported

So for now (until I can find another solution) I'll have to fstrim the disk under Ubuntu.