Running OS lion from USB memory stick

How can I tell which USB memory stick will be fast enough to run OS X Lion from. The HDD on my rev A MacBook Air is showing up in disk utility in red, it says this disk has a fault which cannot be repaired, please backup a seek assistance, though it has been showing this for over a year I assume it will go pop eventually. I have tried running lion from a portable HDD but having this hanging off the side it loses portability ,and this drains the battery, due to age I think putting a new drive in is more hassle than its worth, and finding a SSD at a reasonable price seems hit and miss, whether the one you order will work with a rev A . I have tried 1 or 2 memory sticks they have worked but been quite laggy due to speed. Any advice would be greatly appreciated.

Edited by janitor (Mon 04-Nov-13 20:24:32)

If putting a new hard disk in is more hassle than its worth, why even consider an SSD? Anyway, although I think that any USB stick is going to be too slow, here's a comprehensive list:

http://usbspeed.nirsoft.net/

Thank you for that, the bit about HDD being to much trouble was probably a bad choice of words, removing and replacing the HDD looks from reading about it, a complex job with no performance gain.

You can find new m4 ssds on eBay for reasonable prices.

A MacBook Air Rev A uses a 1.8inch PATA drive. Even if you could somehow shoehorn an M4 into it it wouldn't work.

I did find a reasonably priced SSD on amazon, but reading the reviews,there are two SSDs with almost identical model numbers, and it's hit and miss if you get the macbook compatible one, one extra letter on the end of the model number is a sign of which model it is.