I have two external USB 3.0 SSD drives from Samsung (one is Model T1, other T3).

I would like to trim them with my Ubuntu 16.04.1 LTS.

While doing that I receive a error message. Here an example:

sudo fstrim -v  /media/techo/Samsung_T3
fstrim: /media/techno/Samsung_T3: the discard operation is not supported

But the device support the TRIM Command:

techno@server:~$ sudo hdparm -I /dev/sdb |grep -i TRIM
       *    Data Set Management TRIM supported (limit 8 blocks)

thx. What do I wrong?


  • 1
    fstrim via USB is not supported as discussed extensively here: ubuntuforums.org/showthread.php?t=2315800 – WinEunuuchs2Unix Dec 14 '16 at 17:49
  • Irregardless of whether drive supports trim, when connected thru usb you can't run a trim command as it's a SATA command. Case closed... – doug Dec 14 '16 at 17:52
  • 2
    I don't think so, that USB generally does not support it. Trim should work via USB Attached SCSI Protocol. Question is if USAP is proper implemented in Linux - en.wikipedia.org/wiki/USB_Attached_SCSI – Luckyrings Dec 15 '16 at 19:39
  • 2
    Maybe fstrim does not support USAP. But the Samsung SSD T3 Portable drive support USAP. While in Windows 8+ it connects with USB Attached SCSI (UASP), enabling advanced functionality like NCQ and TRIM (SCSI Unmap). So what about Linux now? – Luckyrings Dec 15 '16 at 19:45
  • 4
    I second that. Trim works over USB and should definitely work on linux. The attitude of the user @doug is really unacceptable. – Pa_ Aug 6 '17 at 16:09

USB drives use a USB<>SATA translation via an IC. Different ICs offer slightly more or less SATA command translations. They all translate the SATA commands required for typical disk usage.

So, the hdparm -I (inquiry) command will work. It will tell the user that 'trim' is supported. But that doesn't mean the USB<>SATA translation includes translating the trim command.

It isn't that the inquiry -I command gives incorrect information. The USB<>SATA translation chip just isn't designed to translate the trim command. If enough users complain, something might be done to make the translations more complete.

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