In case A in Figure 12-4, clients accessing two different database servers use one network card. That means that clients accessing Servers A and B have to compete over the network and past the network card. In the case B, clients accessing Server A use a different network card than clients accessing Server B.
It would be even better to put your database servers on different machines. You may also want to put heavy users of different databases on different machines.
Figure 4-2: Isolating heavy network users
