I just bought a new iMac (late 2015) with an internal 1 tb SSD as the main drive. However, I want to preserve as much space as possible on the drive, so I am considering using an external SSD to store my iMovie and Photos libraries. I want it to be an SSD so it is still fast, but I also was considering using a USB3 enclosure due to the cost of Thunderbolt drives or enclosures. I've read that USB3 doesn't support the use of TRIM. My question is, is TRIM necessary if my SSD is not a boot drive? If I don't have it, will it degrade the performance of the SSD in this application? Thanks for any help you can provide.