Nortel Networks WEB OS 212777 - Manual (Page 131)

Web OS 10.0 Application Guide
Chapter 6: Server Load Balancing n 131
212777-A, February 2002
Metrics for Real Server Groups
Metrics are used for selecting which real server in a group will receive the next client connec-
tion. The available metrics
minmisses (minimum misses), hash , leastconns (least con-
nections), roundrobin , bandwidth , and response (response time) are explained in
detail below. The default metric is leastconns .
To change a real server group metric to minmisses , for example, enter:
Minimum Misses
The minmisses metric is optimized for Application Redirection. It uses IP address informa-
tion in the client request to select a server. The specific IP address information used depends on
the application:
n
For Application Redirection, the client destination IP address is used. All requests for a
specific IP destination address is sent to the same server. This metric is particularly useful
in caching applications, helping to maximize successful cache hits. Best statistical load
balancing is achieved when the IP address destinations of load-balanced frames are spread
across a broad range of IP subnets.
n
For SLB, the client source IP address and real server IP address are used. All requests
from a specific client are sent to the same server. This metric is useful for applications
where client information must be retained on the server between sessions. With this met-
ric, server load becomes most evenly balanced as the number of active clients with differ-
ent source or destination addresses increases.
When selecting a server, the switch calculates a score for each available real server based on
the relevant IP address information. The server that scores the highest is assigned the connec-
tion. This metric attempts to minimize the disruption of persistency when servers are removed
from service. This metric should be used only when persistence is a must.
N OTE – The minmisses metric cannot be used for firewall load balancing, since the real
server IP addresses used in calculating the score for this metric are different on each side of the
firewall.
>> # /cfg/slb/group <group number> (Select the real server group)
>> Real server group# metric minmisses (Use minmisses metric)