The Workload Manager can facilitate the process of consolidating
multiple source systems onto a target system. You can use workgroups
to help you plan and execute the consolidation, and to manage the final
consolidated system.
To partition the workload on the target system |
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One typical concern regarding consolidation is the limited amount of control
the system manager has over the target system. Before the introduction
of the Workload Manager, five scheduling subqueues were available on each
of the source systems, and only five scheduling subqueues were available on
the target system. As a result, the scheduling subqueues on the consolidated
system contain a larger numer and varieity of processes than
did the source systems, which decreased the system manager's ability to
control CPU scheduling.
With the introduction of the Workload Manager, you can now define
multiple workgroups to represent the users of each of the source systems. For
example, suppose you are consolidating three systems. In this case, you could
create workgroups to represent the CS, DS, and ES processes
from each one, for a total of nine workgroups on the target system. This
preserves the partitioning that had been available with the physical separation
of the source systems.
Alternatively, you can use the Workload Manager to define workgroups that more
naturally reflect the needs of the combined user population. Perhaps data
entry clerks had been in the CS subqueue of several source systems and now you
can combine them into a single workgroup on the target system. You might
collect similar batch jobs into a common workgroup. Or, you could separate
users who were once forced to share the CS subqueue into distinct workgroups.
The scheduling characteristics of the workgroups on the target system can be
adjusted to result in the CPU access that the system manager requires to
achieve desired performance.
To manage user expectations |
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Another area of concern relates to the effect of the consolidation itself
on user's experience and expectations of system performance.
Consider a situation where you are consolidating Systems A, B, and C onto
System D over a period of time. You plan to bring over System A on the
first weekend, System B on the second weekend, and System
C on the final weekend. During the first week on the target system,
while the first set of users is running alone on System D, the response time
and throughput are excellent. When they are joined by the users from System B,
their performance may degrade. Once all three systems are combined on the
target, the System A users may actually complain about their performance. Even
though it may be better than what they had on System A, the performance
degraded as additional users were added to System D.
How can the Workload Manager be used to help this situation?
The first set of users on the target system grew dissatisfied because they had
become accustomed to the better performance when they had exclusive use
of the target system. To solve this problem, you can restrict the amount
of CPU available to users. For example, constrain System A users to
30% of the target system so that they will experience, from the onset, the
performance that will result when the entire consolidation is complete.
This example is obviously simplified. You may not wish to
divide the target system up evenly among the users from the three source
systems. Perhaps one set of users is more important and requires more of the
CPU. Alternatively, the consolidation may raise the larger concern of how
to ensure satisfactory coexistence of competing workloads from the various
source systems once they have been consolidated. The Workload Manager
gives you the tools you need to create an effective workgroup configuration,
monitor the performance, and make adjustments as necessary to ease the
consolidation process.
