Brocade Virtual ADX Global Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 165)

Brocade Virtual ADX Global Server Load Balancing Guide 155
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Advanced GSLB configuration for IPv6
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To change the session-table capacity metric, enter commands such as the following:
Virtual ADX(config)#gslb policy
Virtual ADX(config-gslb-policy)#capacity threshold 99
Syntax: [no] capacity threshold num
The num parameter specifies the maximum percentage of a site ADX device’s session table that
can be in use. If the ADX device’s session table utilization if greater than the specified percentage,
the GSLB Brocade Virtual ADX prefers other sites over this site. You can specify a percentage from
0-100. The default is 90.
To change the session-table tolerance metric, enter commands such as the following:
Virtual ADX(config)#gslb policy
Virtual ADX(config-gslb-policy)#num-session tolerance 20
Syntax: [no] num-session tolerance num
The num parameter specifies the maximum percentage by which the session table utilization on
ADX devices at different sites can differ without the GSLB Brocade Virtual ADX selecting one over
the other based on this metric. You can specify a tolerance from 0-100. The default is 10.
FlashBack speed metric
If multiple sites compare equally based on all the metrics above, the Brocade Virtual ADX chooses
a site as the best one based on how quickly the GSLB Brocade Virtual ADX received responses to
health checks to the site ADX device.
The GSLB Brocade Virtual ADX uses a tolerance value when comparing the FlashBack speeds of
different sites. The tolerance value specifies the percentage by which the FlashBack speeds of the
two sites must differ in order for the Brocade Virtual ADX to choose one over the other. The default
FlashBack tolerance is 10%. Thus, if the FlashBack speeds of two sites are within 10% of one
another, the Brocade Virtual ADX considers the sites to be equal. However, if the speeds differ by
more than 10%, the Brocade Virtual ADX prefers the site with the lower FlashBack speed.
FlashBack speeds are measured at Layer 4 for all TCP/UDP ports. For the application ports known
to the Brocade Virtual ADX, the FlashBack speed of the application is also measured.
When the Brocade Virtual ADX compares the FlashBack speeds, it compares the Layer 7
(application-level) FlashBack speeds first, if applicable. If the application has a Layer 7 health
check and if the FlashBack speeds are not equal, the Brocade Virtual ADX is through comparing the
FlashBack speeds. If a host is associated with multiple applications, the GSLB Brocade Virtual ADX
uses the slowest response time among the applications for the comparison. However, if only the
Layer 4 health check applies to the application, or if further tie-breaking is needed, the Brocade
Virtual ADX then compares the Layer 4 FlashBack speeds.
You can modify the following FlashBack parameters:
• Application tolerance
• TCP tolerance