All of us accessing the board at the same time uses more memory than the board cache has, so it has to shut down temporarily to bring it's memory back up.
The only thing that could possibly fix it, would be to erase about half the stuff on all of the board.
That doesn't do anything - the board crashes because too many people are accessing the server for it to handle the processing.
It has nothing to do with how much data is stored on the server's hard drive.