I was trying to backup many files (~10,000) from a hard drive on an OS-less notebook to an external 500 GB HDD, so I booted up the Fedora 22 Live XFCE spin using a USB, started the copy and after 5 minutes or so, the whole system froze, I was able to move the cursor and all, but I wasn't able to cancel the copy, open a console, start another tty (though I was able to change TTY by CTRL+ALT+FX, but no login prompt showed, only a blank screen with a blinking cursor), as if the USB from which I booted was "locked". This happens EVERY time, with EVERY different USB port, and I was able to reproduce it on many many different computers and brands (10+). The only way I am able to copy any amount of files is by using rsync, but why does this happen? How can I work around it?
Just to clarify things a little bit, the Live USB media is a 4 GB USB 2.0 pen drive with a 500 MB home partition and a 1 GB persisten storage area. The external backup media is a USB 2.0 HDD. Both have access indicator LEDs that blink when I/O is occurring, neither seem to blink while the computer freezes, as if both were disconnected altogether.