What are the different load-balancing methods and how do they work?

The Ratio load balancing method

When you configure a pool to use the Ratio-Member load balancing method, DNS Load Balancer performs load balancing requests across the pool members based on the weight assigned to each pool member (virtual server). The system uses pool member weight as a percentage of the total of the weights of all the members assigned to the pool to determine the frequency at which a pool member receives connection requests.

Consider the fictional company SiteRequest, where the wide IP www.siterequest.com contains a pool named poolMain. This pool contains three members, with the following weight assignments:

Virtual Server 1: weight 50

Virtual Server 2: weight 25

Virtual Server 3: weight 25

Each time DNS Load Balancer selects this pool, it load balances across all three members. Over time, the load balancing statistics for this pool appear as follows:

Virtual Server 1: selected 50 percent of the time

Virtual Server 2: selected 25 percent of the time

Virtual Server 3: selected 25 percent of the time

Use Ratio when you want to send ttwice as many connections to a faster server and half as many connections to a slow server.

The Round-Robin load balancing method

The Round Robin load balancing method distributes DNS name resolution requests in a circular and sequential pattern among the virtual servers in a pool. Over time, each virtual server receives an equal number of connections.

Use Round Robin when you want to distribute requests equally among all virtual servers in a pool.

The Static Persist load balancing method

The Static Persist load balancing method uses the persist mask, with the source IP address of the LDNS, in a deterministic algorithm to send requests to a specific pool member (virtual server). Using this method DNS Load Balancer sends DNS name resolution requests to the first available pool member based on a hash algorithm that determines the order of the pool members. This algorithm orders the pool members differently for each LDNS that is sending requests to DNS Load Balancer, taking into account the Classless Inter-Domain Routing (CIDR) of the LDNS. As DNS Load Balancer distributes requests across all pool members, requests from each LDNS (and thus, each client) are generally sent to the same pool member. When the selected pool member becomes unavailable, DNS Load Balancer sends requests to another pool member. When the original pool member becomes available again, DNS Load Balancer sends requests to that pool member.

Use Static Persist when you want requests from a specific LDNS to resolve to a specific virtual server.