OS is Windows 8.1 Pro x64 on both my desktop and laptop. I keep my digital images on an SSD in an external USB3 enclosure, because I transfer images to the drive and work on the images when I'm at home on the desktop and also when travelling with a laptop - both machines have USB3 ports. The problem I have is that both dfrgui and command line defrag detect the SSD as an HDD. I've disabled scheduled optimisation on the drive in dfrgui to prevent normal HDD defrag being run on it, but is there any way to run TRIM against the drive? When I try to run defrag /l against the drive, I just get an error back:

C:\WINDOWS\system32>defrag /L P:
Microsoft Drive Optimizer
Copyright (c) 2013 Microsoft Corp.

Invoking retrim on PHOTOS (P:)...

        Retrim:  100% complete.

The operation requested is not supported by the hardware backing the volume. (0x8900002A)