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First of all, I am pretty surprised my usb flash device supports trim:

sudo  hdparm -I /dev/sdb | grep 'Model\|TRIM' 

gives me:

Model Number:       SanDisk SSD CZ80 32GB                   
   *    Data Set Management TRIM supported (limit 8 blocks)
   *    Deterministic read data after TRIM

The usb stick is formatted with ext4. So according to hdparm, trim should work. However when I switch to the device and run:

sudo fstrim ./

it gives me:

fstrim: ./: FITRIM ioctl failed: Operation not supported

So what could be the issue here? Does hdparm lie about trim support, or could there be an other issue? Who to ask to debug such issues? (Info: fstrim works very well with my internal ssd).

Full output of hdparm -I /dev/sdb can be found here:

share|improve this question
only ext4 supports trim so what is the current formatting of the usb disc? – Rinzwind Feb 16 '14 at 16:48
you are wrong: btrfs also supports trim. Apart from that I have stated "The usb stick is formatted with ext4" – GEO Feb 16 '14 at 16:59

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