Brocade Communications Systems ServerIron ADX 12.4.00 User Manual

Global Server Load Balancing overview

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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