Originally Posted by ~***********~
Sometimes MySQL server is located on the same server, sometimes not. And that is influence on the speed for sure.
I have seen speed effected if a MySQL server is connected to a webserver over the public side of the network. I once had an MS SQL server in another DC (part of the Planet). The DC's were in the same town but just a few more milliseconds on a ping slowed things right down.
When connecting a MySQL or MS SQL server to a web server I find the best performance is over a private network from Server 1 to a switch to server 2 both on secondary NIC's. Anything different just kills performance in the network side of things.