I don't know every single one personally...I do know a number of them. I don't believe there are any here that I am not aware of.
[Small sigh]
It doesn't take that much blood to sate thirst, and you'd be surprised how quickly the body replenishes. Beyond that there are many different individuals here.
Besides, some vampires here don't even require actual blood. And for the others, the general rule is that they only require living blood. Not necessarily human.