Coyote Point Systems E350GX, Руководство по установке и администрированию

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Managing Servers
Equalizer Installation and Administration Guide 147
Using Outbound NAT on a Server IP in Multiple Clusters
Servers are identified in the NAT daemon configuration file by their IP addresses. If a server IP address is listed
more than once in the file, it is the
last NAT setting listed in the file that takes effect for that server IP.
This means that:
• If the same server IP address is used in more than one cluster, then changing the outbound NAT setting for
one of the server instances to anything other than
Default address
changes the NAT IP address for all the
instances of that server in all clusters.
• If the outbound NAT setting for one of the instances of a server is subsequently changed to something other
than the default, then the new setting takes effect for all instances of the server in all clusters.
Adjusting a Server’s Initial Weight
Equalizer uses a server’s initial weight as the starting point for determining the percentage of requests to route to
that server. As Equalizer gathers information about the actual performance of a server against client requests, it
adjusts the server’s current weight so that servers that are performing well receive a higher percentage of the cluster
load than servers that are performing at a slower rate.
When you install servers, set each server's initial weight value in proportion to its “horsepower.” All the initial
weights in a cluster do not need to add up to any particular number;
it’s the ratio of the 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 initial weights of these servers to 100 and 50 is equivalent to
setting the initial weights to 180 and 90.
Values for server weights can be in the range 0-200, with 0 meaning that no new requests will be routed to the
server, essentially disabling the server for subsequent requests. In general, you should use higher initial 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 initial 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 initial 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 initial weights of the servers in the cluster based on their performance.
Setting initial Weights for Homogenous Clusters
If all the servers in a cluster have the same hardware and software configurations, you should set their initial weights
to the same value initially. We recommend that you use a initial weight of 100 and set the load-balancing response
parameter to
medium .
As with any new configuration, you will need to monitor the performance of the servers under load for two to three
hours. If you observe that the servers differ in the load they can handle, adjust their initial weights accordingly and
again monitor their performance. You should adjust server weights by small increments; for example, you might set
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.