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Capacity planning is the function of projecting resource requirements for a workload or an installation to assure that sufficient resources are available to perform required work; in traditional mainframe environments, being a capacity planner is often a very important career position in an IT organization.
However, when servers began being implemented on low-cost platforms instead of on mainframes, it became less expensive to buy a new server rather than spend the time and resource for tuning. Upgrades did not have to be planned months or years in advance, but in days or weeks.
Now, with the consolidation technique of moving smaller servers back to the mainframe, often under z/VM, capacity planning is again a requirement. Sometimes in the pressure of the moment, we are tempted to "guess and go". A better approach is to collect performance data for a period of time, analyze the requirements, and then use that data to calculate requirements on the z/VM platform.
Projecting capacity requirements from an Intel-based server to a mainframe can be done. Using the "4" megaHertz-to-MIP estimator (Barton's number, as presented at SHARE and the IBM Technical Conference ) is one methodology. This methodology takes the resource requirements on Intel in terms of MHz, divides that by 4, and that provides the MIP requirement. This is not exact, but is easily duplicated by any installation testing their consolidation plan. For example, if an application required 20% of a 1 GHz Intel processor, then it would take about 50 "MIPS" of a mainframe. This should provide a conservative estimate in size of processor required.
Each subsystem can be evaluated using a similar process. Using this methodology, installations have the ability to size existing workloads and build their own capacity model based on their experiences.
An initial capacity planning estimate for a Domino workload on Linux on zSeries is available through your IBM marketing representative. They can request a sizing questionnaire from IBM TechXPress, complete the questionnaire with your help, and submit it. TechXPress will route it to the department that does the sizings for Domino on zSeries.
The following types of information are needed to complete this form:
Number of registered users
Number of connected users
Peak number of active users in a 15 minute period by usage pattern (light, medium, heavy, power) and client type (Notes, iNotes, POP3, IMAP, Webmail)
Exploited functions/features of Domino: clustering, full-text indexing, personal agents, Message Tracking, local replicas, port encryption, network compression, SSL, and so on
Projection of future mail growth
Description of current production environment
Requirements for third-party tools, like anti-virus
Upon receipt of the completed questionnaire, the sizer will perform the capacity sizing and then provide the marketing representative with an estimate of the processor size you will need to support this workload. IBM employees can submit a TechXpress request on the IBM intranet or by phone. Find out more at this Web site:
Barton Robinson, one of the redbook authors, is the founder of Velocity Software. See 12.2 for a brief description of their toolkit.
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