The diglloyd.com photography workload includes frequent creation of large files, typically 1-5GB, but sometimes up to 14GB (saved sizes). A sample is shown below. To save and open those big files fast requires a very fast drive (and configuring Photoshop preferences for speed).
The internal SSD (flash storage) in the 2013 Mac Pro is stunningly fast and that is a great option. But it also has other uses, and it’s great to have fast external SSD performance as well, particularly if one did not opt for the 1TB internal flash.
To match the internal 2013 Mac Pro flash storage speed externally requires Thunderbolt 2 connectivity to fast SSDs.
To that end, diglloyd.com photography is now using dual 960GB OWC Mercury Accelsior E2 PCIe SSDs in a RAID-0 stripe configuration for a 1.92TB working volume. The enabling device is the OWC Mercury Helios 2 enclosure, into which those two cards is installed. It works great and the fan noise is quite low.
Performance of that striped-SSD configuration is around 1000 MB/sec for writes and 1100MB/sec for reads for sustained transfers, with somewhat higher speeds in shorter bursts.