Compaq AA-Q88CE-TE - Manual (Page 26)

Starting and Setting Up RTR
2.5 Setting up Callout Servers
Example 2–5 Configuration of Callout Servers
% rtr
RTR> set environment/node= -
_RTR>
(FE1,FE2,FE3,TR1,TR2,BE1,BE2,BE3)
RTR> start rtr
RTR> create facility funds_transfer/frontend=(FE1,FE2,FE3) -
_RTR>
/router=(TR1,TR2) -
_RTR> /backend=(BE1,BE2,BE3) -
_RTR> /call_out=router
2.6 Router Load Balancing
Router load balancing, or intelligent re-connection of frontends to a router
is possible, allowing a frontend to select the router that has least loading. The
create facility and set facility commands have the /balance qualifier to
control this. RTR now allows frontends to determine their router connection. The
RTR version 2 implementation of load balancing treated all routers as equal and
this could cause reconnection timeouts in geographically distant routers.
When used with create facility , /balance specifies that load balancing is
enabled for frontend/router connections across the facility.
Use the set facility/[no]balance to switch load-balancing off and on.
The default behavior (/nobalance) is for a frontend to connect to the preferred
router. Preferred routers are selected in the order specified in the
create
facility/router=tr1,tr2,tr3.. qualifier. Automatic failback ensures that the
frontend will reconnect to the first router in the order when it becomes available.
Manual balancing can be attained by specifying different router orders across the
frontends.
Non load-balanced frontend connections will fail back to the preferred router
when it becomes available.
Automatic load balancing institutes a router list with a random value for the
frontend assigned at the time the
create facility with the /balance command
is issued. The frontend will sort the list of routers based on its own random order.
Randomness ensures that there will be a balance of load in a configuration with a
large number of frontends. Automatic failback will maintain the load distribution
on the routers and failback is controlled at a limited rate so as not to overload
configurations with a small number of routers.
The following points should be born in mind when using load-balancing:
• Frontends connect to a single router, per facility
• When several routers are configured on the frontend:
The specified list in the create facility constitutes the preferred search
order, by default, unless /balanced is used
• Balancing may be individually enabled or disabled on the frontend nodes.
• Balancing is dynamic. The loss or addition of a router node causes the
frontend nodes to redistribute their connections.
2–8 Starting and Setting Up RTR