12 ServerIron ADX Global Server Load Balancing Guide
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Global Server Load Balancing overview
1
Use the round robin selection metric instead of the least response selection metric when you want
to prevent the GSLB ServerIron ADX from favoring new or recently recovered sites over previously
configured active sites. The Least Response metric can cause the GSLB ServerIron ADX to select a
new site or a previously unavailable site that has come up again instead of previously configured
sites for a given VIP. This occurs because the GSLB ServerIron ADX has selected the new site fewer
times than previously configured sites for the VIP.
In some cases, the least response selection metric can cause the GSLB ServerIron ADX to send
client requests to a new or recovered site faster than the site can handle while it is coming up. To
avoid this situation, you can configure the GSLB ServerIron ADX to use the round robin selection
metric instead of the least response selection metric as the final tie breaker.
The round robin selection metric is disabled by default.
Check the current and maximum values for GSLB resources using the show gslb resource CLI
command.
If you are configuring more than 256 zones or configuring more than 600 hosts, perform the
following tasks.
1. Change the maximum virtual server system parameter to the maximum value supported in the
current release. Use the l4-virtual-server command.
For the current maximum virtual server value supported, see the table named "The Number of
Supported Real Servers, Virtual Servers and Ports" in the ServerIron ADX Server Load
Balancing Guide.
2. Change the maximum real server system parameter to the maximum value supported in the
current release. Use the l4-real-server command.
For the current maximum real server value supported, see the table named "The Number of
Supported Real Servers, Virtual Servers and Ports" in the ServerIron ADX Server Load
Balancing Guide.
3. Change the maximum server port parameter to the maximum value supported in the current
release. Use the l4-server-port command.
For the current maximum server port value supported, see the table named "The Number of
Supported Real Servers, Virtual Servers and Ports" in the ServerIron ADX Server Load
Balancing Guide.
4. Check your system parameter values using the show default value CLI command.
ServerIronADX# show gslb resources
GSLB resource usage:
Current Maximum
sites 0 128
SIs 0 200
SIs' VIPs 0 2048
dns zones 0 1000
dns hosts 0 1000
health-checks app. 0 1000
dns IP addrs. 0 2048
affinities 0 1024
affinity groups 0 128
static prefixes 0 250
user geo prefixes 0 512
prefix cache 0 11786
RTT entries 0 10000
GSLB host policies 0 100
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