> I was looking on FaceBook 'sDATA storage and MySQL !!!
>
> For sure millions simultaneous Users connected !!!

I would guess nobody is running an database server with millions of
connections simultaneously open.

On huge Systems as Facebook there are some application servers between
users and database which do serialize database access to an lower number
of connections - it does not make sense to let DB server process
millions of queries simultaneously since the hardware has not that much
parallelity.

Elmar