Brocade Virtual ADX Server Load Balancing Guide (Supporting ADX v03.1.00) User Manual
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Brocade Virtual ADX Server Load Balancing Guide
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Overview
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If you set the weight so that your fastest server gets 50 percent of the connections, it will get 50
percent of the connections at a given time. Because the server is faster than others, it can
complete more than 50 percent of the total connections overall, because it services the
connections at a higher rate. Therefore, the weight is not a fixed ratio but adjusts to server capacity
over time.
The difference between weighted and enhanced-weighted load-balancing is the method of
distributing the traffic after it is assigned.
Connection assignments with weighted predictor for weighted load-balancing
In weighted load-balancing, the traffic is distributed by allocating all of the required connections
sequentially to the server with the greatest weight first and then to the server with the next greatest
weight, followed by the server with the next greatest weight and so on, until all servers have
received their share of connections. The process then repeats.
shows the distribution pattern for Weighted Load-Balancing in an example configuration
with three real servers, A, B, and C. Real Server A has a weight of 1, Real Server B has a weight of
2, and Real Server C has a weight of 3. The numbers in bold indicate which server receives the new
connection. When the weighted predictor is configured, connections are assigned as shown in
.
TABLE 4
SLB with the weighted predictor
Real Server A
Real Server B
Real Server C
weight = 1
weight = 2
weight = 3
Connections
Server load
a
a.
For the weighted predictor, the server load is calculated as connections divided by server weight = server load.
Fractional remainders are rounded down. If there is a tie, the server with the highest weight receives the connection
Connections
Server load
Connections
Server load
0
0 / 1 = 0
0
0 / 2 = 0
0
0 / 3 = 0
0
0 / 1 = 0
0
0 / 2 = 0
1
1 / 3 = 0
0
0 / 1 = 0
0
0 / 2 = 0
2
2 / 3 = 0
0
0 / 1 = 0
0
0 / 2 = 0
3
3 / 3 = 1
0
0 / 1 = 0
1
1 / 2 = 0
3
3 / 3 = 1
0
0 / 1 = 0
2
2 / 2 = 1
3
3 / 3 = 1
1
1 / 1 = 1
2
2 / 2 = 1
3
3 / 3 = 1
1
1 / 1 = 1
2
2 / 2 = 1
4
4 / 3 = 1
1
1 / 1 = 1
2
2 / 2 = 1
5
5 / 3 = 1
1
1 / 1 = 1
2
2 / 2 = 1
6
6 / 3 = 2
1
1 / 1 = 1
3
3 / 2 = 1
6
6 / 3 = 2
1
1 / 1 = 1
4
4 / 2 = 2
6
6 / 3 = 2
2
2 / 1 = 2
4
4 / 2 = 2
6
6 / 3 = 2
2
2 / 1 = 2
4
4 / 2 = 2
7
7 / 3 = 2
2
2 / 1 = 2
4
4 / 2 = 2
8
8 / 3 = 2