Nortel Web OS 10.0, Application Manual

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Web OS 10.0 Application Guide
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Chapter 6: Server Load Balancing
212777-A, February 2002
Weights for Real Servers
Weights can be assigned to each real server. These weights bias load balancing to give the fast-
est real servers a larger share of connections. Weight is specified as a number from 1 to 48.
Each increment increases the number of connections the real server gets. By default, each real
server is given a weight setting of 1. A setting of 10 would assign the server roughly 10 times
the number of connections as a server with a weight of 1. To set weights, enter the following
commands:
N
OTE
– Weights are not applied when using the
hash
or
minmisses
metrics.
Connection Time-outs for Real Servers
In some cases, open TCP/IP sessions might not be closed properly (for example, the switch
receives the
SYN
for the session, but no
FIN
is sent). If a session is inactive for 10 minutes (the
default), it is removed from the session table in the switch. To change the time-out period,
enter the following:
The example above would change the time-out period of all connections on the designated real
server to four minutes.
Maximum Connections for Real Servers
You can set the number of open connections each real server is allowed to handle for SLB. To
set the connection limit, enter the following:
Values average from approximately 500 HTTP connections for slower servers to 1500 for
quicker, multiprocessor servers. The appropriate value also depends on the duration of each
session and how much CPU capacity is occupied by processing each session. Connections that
use a lot of Java or
CGI
scripts for forms or searches require more server resources and thus a
lower
maxcon
limit. You may wish to use a performance benchmark tool to determine how
many connections your real servers can handle.
When a server reaches its
maxcon
limit, the switch no longer sends new connections to the
server. When the server drops back below the
maxcon
limit, new sessions are again allowed.
>> # /cfg/slb/real
<real server number> (Select the real server)
>> Real server# weight 10
(10 times the number of connections)
>> # /cfg/slb/real
<real server number> (Select the real server)
>> Real server# tmout 4
(Specify an even numbered interval)
>> # /cfg/slb/real
<real server number> (Select the real server)
>> Real server# maxcon 1600
(Allow 1600 connections maximum)