In general, sustained throughput on Thunderbolt used for PrPro is actually quite a bit more than with USB3. So the comment " ... are easily 2.5 to 3 times as fast ... " has me puzzled. Three times as fast as ... what?
First, I'd suggest checking the hardware forum for questions on this ...
And of course, it's always nice if Bill Gehrke pops in, as he is The Dude for such info.
Well, I am not sure I can add much to a Mac problem. As I am a PC user I rely on different benchmarks. I will say this, there are great performance differences of SATA III to USB 3 convertors and even USB 3.0 ports.
Latency's on USB devices with video is very real, and does very with the implementation.
Let me relate my successful experiment with my laptop using a Samsung T1 USB 3.0 Flash Drive. I am easily/smoothly editing XAVC S 4K 100 Mbits/second (probably simpler than your Red video) with all the project files and media on this device with no problems . Samsung now has a newer T3 which might be slightly better. The tested sequential read/write performance is ~400 MB/second. as you can see below:
Thank you for your responses fellas. I think after deep research the problem just lies in my CPU. I have the low end of the late 2014 27" iMac Retina. It's i5 with a 2GB AMD GFX Card. I guess I expected the SSD to accelerate my 4k Editing speeds, but it really perhaps just lies in the internals of my computer.
R Neil Haugen wrote:
So the comment " ... are easily 2.5 to 3 times as fast ... " has me puzzled. Three times as fast as ... what?
The OP meant to say that the USB 3.0-connected SSD is three times as fast as the Thunderbolt-connected hard drive. This is because hard drives are themselves limited in their sustainable (sequential) transfer speed by their physically spinning platters. In fact, the average sequential transfer speed of a single typical 7200 RPM hard drive is only about 160 MB/second while SSDs (via a USB 3.0 connection) can sustain about 400 MB/second.