Specifications

Managing Servers
Equalizer Installation and Administration Guide 91
assigned server weight for a server to the total of all the server weights that determines the amount
of traffic sent to a server.
For example, you might assign a server with 4 dual-core 64-bit processors operating at 3.40GHz a
value of 100 and a server with 2 dual-core 64-bit processors operating at 1.86GHz a value of 50.
The first server will initially receive approximately 66% (100 divided by 150) of the traffic. The
second server will initially get about 33% (50 divided by 150) of the traffic. It’s important to note
that setting the static weights of these servers to 100 and 50 is equivalent to setting the static
weights to 180 and 90.
If Equalizer is performing adaptive load balancing (ALB), you should generally use higher static
weights. When you have enabled Equalizer’s ALB feature (that is, the load balancing policy is not
set to round robin or static weight), using higher static weights will produce finer-grained load
balancing. Higher weights enable Equalizer to adjust server weights more gradually; increasing the
weight by 1 produces a smaller change if the starting weight is 100 than it does if the starting weight
is 50.
However you set the static weights, Equalizer will adjust the weight of servers dynamically as
traffic goes through the cluster. Dynamic server weights might vary from 50-150% of the statically
assigned values. To optimize cluster performance, you might need to adjust the static weights of the
servers in the cluster based on their performance.
To change a server’s static weight (see Figure 45), follow these steps:
1. Log into the Equalizer Administration Interface in edit mode.
2. In the left frame, click the name of the server to be modified. The server’s parameters appear in
the right frame.
3. Select Change Server Parameters from the local menu. The modify server screen opens in the
right frame.
Figure 45 Changing a server’s static weight
Note – Equalizer stops dynamically adjusting server weights if the load on the cluster drops
below a certain threshold. For example, if web traffic slows significantly at 4:00 AM PST,
Equalizer will not modify server weights until traffic increases again. Because a server’s
performance characteristics can be very different under low and high loads, Equalizer optimizes
only for the high-load case. Keep this in mind when you configure new Equalizer installations; to
test Equalizer’s ALB performance, you’ll need to simulate expected loads.