Who needs SLB?
If you have more than one server providing the same services to end users, you should use SLB to distribute traffic to those servers. Besides redistributing traffic in the event of a server failure, the SLB device can also allow you to gracefully take a server “out of service” for maintenance. Adding additional servers is also very simple. Simply add the new servers to the SLB config and they will automatically added to the server pool.