I have a number of slightly differently configured Raspberry Pi systems. On most of them, when I type "fstrim -v /" I get something like this:
fstrim -v / /: 122716160 bytes were trimmed
This command tells the SD card which blocks have been written to but are no longer used, so that it can erase them for future use. I normally put this command in /etc/rc.local and/or a weekly cron job.
Yesterday I got a new Pi, loaded it with 2013-09-25-wheezy-raspbian.img and on this one I get:
fstrim -v / fstrim: /: FITRIM ioctl failed: Operation not supported
I looked around an saw references to the kernel not supporting it, problems with encrypted filesystems, volume manager etc. But this Pi has neither of them, and I have others that are running Raspbian as well with the same latest kernel.
What can be the reason for this? Can it be related to the particular SD card in use? (it is a Transcend 16GB)