IBM Enterprise Workload Manager Release 1

188 IBM Enterprise Workload Manager

7.1 EWLM and workload balancing overview

The EWLM domain manager has a global view of all the servers and middleware

technologies which make up the management domain that supports the business

applications, as described in 1.2.1, “Domain manager” on page 6. The domain manager

obtains performance information on each server and application instance, and knows how

much time a request is spending at each instance. The domain manager can use this

knowledge to influence network routing decisions made by a load balancer in order to

achieve the end-to-end business response time goal.

Without EWLM, when incoming requests arrive at a load balancer, the load balancer typically

has little information about the application’s health or the performance of the servers it is

routing to. It can use pure algorithmic techniques such as round robin, or general system

statistics represented by static, preconceived weights to route the incoming requests. Some

load balancers have algorithms that allow them to sense network state and forward requests

to the most capable instance, like the instance with the least number of sessions or

connections.

EWLM does not route the work itself, but provides recommendations to the routing entity

using the IBM Server/Application State Protocol (SASP). Through SASP messages a load

balancer can tell the domain manager which systems and applications it wishes to load

balance and the domain manager can make recommendations to load balancers regarding

how to distribute work. However, it is up to the load balancer to actually use EWLM’s

recommendations to route incoming requests to the members. Today, the load balancers that

exploit EWLM are from Cisco Systems Inc. and Nortel Networks.

7.2 Configuring an EWLM load balancing setup

Figure 7-1 shows the components of an EWLM management domain which consists of

managed servers, a domain manager, and a load balancer.

Figure 7-1 EWLM workload balancing components

Although it is assumed that customers who are using EWLM will most likely have

instrumented applications using ARM, the domain manager supports both application-level

Load

Balancer

Domain Manager

Managed ServerManaged Server

Managed ServerManaged Server

Managed ServerManaged Server

Incoming

Requests

Forwarded Requests

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SASP

Communication

EWLM Communication