Questions about BBB

I'm doing a electronic project and I think that BeagleBone Black may be the solution.

The specifications are as follows:
-Linux with PHP or C, for remote connection to mySQL server and TCP / IP sockets for connection to cameras.
-Possibility of digital inputs and outputs and analog inputs, UARTs, PWM,...
-Continuos reading and writing files, up 120kbytes size, at rate of 20Mbits/s on storage medium of at least 32GBytes. A SD card will not work.¿Can I connect an external hard drive to USB 2.0 or other mass storage at 20Mbits/s?
Does anyone has done anything like this?

Reads on an external hard drive ( USB 2.0 ) for me on Debian wheezy are about 10.6 Megabytes / second.

Writes for me on Debian wheezy are about 21 Megabytes / second.

I also did these tests while booted off this external ( USB 2.0 ) hard drive. Which was a Seagate barracuda 7200 RPM drive in a self powered PATA<->USB 2.0 external case. A cheesy / cheap external case at that.