You might want to consolidate several servers’ workloads onto a single server. For example, an organization may have multiple servers located in Los Angles,
Chicago, and New York City. Each cities may even have remote locations in neighboring states. A decision was made to consolidate all of these servers onto one central server in Chicago. The Chicago server would then be responsible for supporting all of the activity in the remote cities. If one wants to know what size server would be needed to support the workloads from all three servers, BEST/1 can help provide the solution.
Consider the following process to consolidate the workloads:
1. As with any BEST/1 model, you will need to build a model for each location using performance data. Refer to “Creating a Model Using Performance Data”
on page 36 for details. This includes the proper method for selecting
representative data, defining the workloads, as well as creating and calibrating each model. Depending on the nature of the business, each model may be built entirely independent of each other, or time differences may need to be
considered. For example, if the business is commodities trading, there is a specific peak period for activity no matter where one is in the country. On the other hand, if the business involves local retail activity, the local time zones and specific life style of the region may dictate another prediction of peak times.
2. Verify the QDEFAULT workload for each system accounts for less than 3% of the system’s total activity. If it accounts for a great deal more than 3%, consider identifying additional workloads until QDEFAULT is left with about 3%. The workload called QDEFAULT is to account for any activity not recorded in any of the other defined workloads.
3. Once each model has been built, consider renaming each of the workloads, with the exception of QDEFAULT. Assume each model had workloads
identified by four departments: Sales, Service, Shipping, and Accounting. These may have been identified by user profiles. Each model would also have a workload called QDEFAULT for any other system activity not recorded in one of these four departments. Rename the workloads so that they can be identified once they are combined. For example, rename the workloads in Chicago to be CSALES, CSERVICE, CSHIPPING and CACCOUNT. New York City could be renamed NYSALES or NYSERVICE. Use option 8 on the Work with Workload menu.
4. Combine all of the workloads into one model. Because all the workloads will be transferred to the Chicago server, start with this workload. After selecting Work with BEST/1 Models (option 1 on the main menu) proceed to Work with Workloads (option 1). From this display, use F6 to add each workload to the Chicago model (one at a time). There would be a total of 13 workloads: three SALES workloads (CSALES, NYSALES and LASALES), three SERVICE workloads, three SHIPPING workloads, three ACCOUNTING workloads, and one QDEFAULT.
5. Because these workloads came from three different servers, the ASPs and Pool assignments, as well as the communication connections, need to be verified.
The following should be checked:
a. Verify all disk activity is in the same ASP b. Verify the system pool numbering scheme
Note: For example, QINTER may have been system pool number 4 in Chicago and system pool number 3 in New York City. Once the workloads are combined make sure all of the activity is occurring in the correct pool. In this case, all of the priority 20 interactive work, is
allocated to system pool number 4 since Chicago had QINTER in system pool number 4. To edit these items, refer to “Working with Functions” on page 76.
c. Check workloads with communication lines associated with them. In this example new communication IOPs and communication lines may have to be created in the consolidated model to handle the New York City and Los Angles workload.
d. Assign the workloads which used communication lines on the separate systems to individual communication lines on the consolidated system.
Refer to “Distribution of Characters Transferred Across Line Resources” on page 170.
6. Verify the model is valid by using F13 on the Configuration menu.
7. Save the model with a different name so to keep each model separate and easily identifiable (using F15 on the Work with BEST/1 Model display). By maintaining separate models, it will be easier for one to reconstruct BEST/1’s results at a future date.
8. Analyze the model and determine the CPU utilization of QDEFAULT. If it does not account for 3% of the combined workload in the consolidated model, it may be desirable to adjust the workloads. The rationale is that as new
workloads are added to the consolidated system QDEFAULT (representing the system overhead) would grow proportionately. In this case, it is feasible to be a little conservative and grow the QDEFAULT workload to slightly exceeded 3%.
This adjustment can be accomplished by using option 2 (Specifying Objectives) or option 7 (Specify Workload Growth) on the Work with BEST/1 Model menu.
Several iterations may be required until the desired level of activity is achieved.
9. The consolidated system model are treated as any other single system model.
You can start growing the workloads to simulate future conditions and analyzing the results for answers to what if scenarios. Refer to “Modeling Workload Growth” on page 110 for modeling projected growth in workloads.
Similarly you would want to analyze several different hardware configurations.
Refer to “Changing System Resources” on page 119 for techniques to change CPU and other system resources.
Note: It is suggested that each time hardware resources are changed, you should save the model under a different name. For example, you may start on model F50 and call it COMBINF50. If you were to then model a configuration 310-2044, it might be called COMB2044. This type of scheme makes it easy to go back to any of the models for any fine tuning in the future.
Chapter 3. Building a Model Using Measured Data 53
Chapter 4. Building a Model Using Predefined Workloads
This chapter describes the predefined workloads that are available with BEST/1, when to use them and how they are accessed. A comparison is given between the workloads that are available with this product and other OS/400 capacity planning tools.