A friend just complained to me about Ubuntu being slow.

Although I've noticed a certain lack of snappiness with Linux vs Windows in the past, I really can't say I've had much to grumble about with the recent distributions of Ubuntu. That said, his objections seem much worse than the ones I used to have and I know that his current setup is significantly more powerful than my laptop.

And then it turned out he is running Ubuntu off an external HDD hooked up via USB2.0. The HD enclosure is USB3.0 but apparently he can't manage to get it to boot on USB3.0 so he switched to one of the USB2.0 ports or whatever and that works, albeit not very well.

Now I would expect USB to add some overhead to communication between the computer and the HDD; SATA is after all designed to get the maximum out of a hard drive, whereas USB is, well, universal.

What are your expreriences with booting off external HDDs?

Edit: Does anybody know just how much of a slowdown can be expected?