I'm trying to run a Parallels VM off of an external drive since my MBA only has a 128GB SSD and the VM takes up nearly 43 GB. I tried a PNY 128GB 3.0 flash drive, and that is essentially hopeless. Windows takes forever to boot. That's despite the fact that BlackMagic speed test shows the flash drive to have write speeds about 25% of the SSD and read speeds of about 50% of the SSD (the Windows load time is MUCH more than 4x what it is off the SSD). Another option to consider is to take a slim USB 3.0 external 2.5" case and put a, say, 64GB SSD inside. That would be bulkier than a flash drive, of course. Is it the device or the USB 3.0 connection is the bottleneck? Would an external SSD run much faster?