User guide

128 ExtremeWarePx1 1.2 Command Reference Guide
Commands for Configuring Servers and Services
The Px-series application switch supports the following scheduling policies:
You may optionally specify a server of last resort for the group. This is a server to which trafÞc is sent if
all the servers in a server-group are down. It could be a server that simply replies to the client with a
"SYSTEM DOWN" message, or a server that can service the request under emergency circumstances
(perhaps a development machine or a system in another geographical location). To specify the server of
last resort, use the optional server-last-resort parameter.
You must use the build command to commit the conÞguration changes made by this command.
Example
This example creates a server group named group1, giving it the weighted least-connections scheduling
policy:
SummitPx1:25 # configure server-group name group1 policy wlc
* SummitPx1:26 # build
This example creates a server group named group2 with round-robin scheduling policy that uses server
with index 9 as its server of last resort:
SummitPx1:27 # configure server-group name group2 policy rr server-last-resort index 9
* SummitPx1:28 # build
Policy Description
round robin Distributes clients evenly across the web server group by passing each new connection
request to the next server in line. The first client connection is sent to the first server,
the second to the second server, and so on, until each server has a connection. When
each server has its first connection, the next client connection is sent to the first server,
the next to the second, and so on.
Round robin is the simplest way of balancing web traffic, and is best suited for
environments in which the performance level of all servers is about equal, and all
servers provide the same content.
weighted round robin Similar to round robin, except that you can apply a weight to each server. For example,
if server A has a weight of two, and server B has a weight of one, server A receives
two connections for each connection given to server B.
Weighted round robin is useful if all servers provide the same content, but some are
faster than others.
least connections Passes a new connection to the server having the fewest active sessions. It distributes
clients based on the server with fewest connections currently open.
The least connections policy provides the best performance under most conditions.
weighted least
connections
As in weighted round robin, assigns a weight to each server. The weight can be based
on a number of things, including:
• Processor speed
• Network connection speed
Connections are distributed using the server with the fewest connections by weight. As
in weighted round robin, weighted least connections can be used if servers have very
different connection-handling capacities.
Weighted least connections has the advantage of not overloading older, slower servers
with too many connections.
hash Selects a server from the group based on a hash value computed from the client IP
address and the service IP address (VIP).