Introduction to the new mainframe: Large-Scale Commercial Computing © Copyright IBM Corp., 2006....

Introduction to the new mainframe:Large-Scale Commercial Computing

© Copyright IBM Corp., 2006. All rights reserved.

Chapter 2: Capacity

2

Introduction to the new mainframe


Chapter objectives

At the end of this chapter you should be able to describe:• Mixed workloads• SLA• PR/SM and LPAR• Parallel Sysplex• Storage concepts and management• Measuring capacity

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Definition of Capacity

Capacity has several definitions:

1. The potential or suitability for holding, storing, or accommodating

2. The facility or power to produce, perform, deploy or, simply process

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Elements required for capacity (1/2)

Any computer system, from a single-user PC to a multi-thousand user IBM System z mainframe performs work in the following stages:

1. Load a program from a storage device, normally a disk, to central storage

2. Process the instructions in the program

3. Load any required data from disk or tape into central storage

4. Process the data and send the results to the desired end point

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Elements required for capacity (2/2)

The relevant components to perform these steps and therefore for capacity estimation & planning are:

Processors Central storage Access input/output storage (for example disk or tape)

Also the network to these devices has to be considered

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Many servers Few Servers

Many servers : Data retention ? Locking across servers ? Connectivity ?

Few servers (IBM System z): Large volumes of data: best in 1 place No rewitting needed of applications 1 total system

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Mixed Workload

The approach to run mixed workload on one single system comes from the fact that in modern processor chips it is very unlikely, in a commercial environment, that one program could keep a processor fully utilized over a longer period of time.

For example, running jobs for Online customers, Online in-house users and Batch work

on the same system.

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Service Level Agreement

A Service Level Agreement (SLA) is an agreement between a service provider and a recipient, generally the server owner and a business unit.

SLAs are the baseline for capacity, availability and performance measurements and ratings.

Example:• 95% of ATM transactions are completed in less than one second.• 90% of daily reports are completed by 6 A.M.

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Managing the system to the SLA

Managing CPU

Managing Disk

Storage concepts (the address space) -> see next slide

Real storage mangement

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Address space

16 megabyte The “Line”

The “Bar” 2 gigabytes

2 terabytes

512 terabytes

16 exabytes

0User Private Area

User ExtendedPrivate Area

Shared Area

User ExtendedPrivate Area

The „Line“ 24 Bit systems The „Bar“ 31 Bit systems

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Architecture, running work & capacity

Program Status Word (PSW) Interrupts

• Machine check• Restart• Program Check• I/O• Supervisor call (SVC)• External

Supervisor call Selection of work to run on a CP Dispatching priority CP utilization balance

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Several servers on 1 physical machine

LPAR

Planning for downtime

• Software

• Hardware

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IBM System z – Parallel Sysplex

ESCON/FICON

Coupling Facility

SYSPLEX Timer

Shared Data

Z9 BC

Z9 EC

Z9 EC

Z9 BC

Parallel Sysplex

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Measurements

Central Processor usage

Central storage usage

Access to disk storage

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Summary

Capacity Complex when you are :

• In a mixed workload• On a large-scale commercial environment

Different workloads different requirements well defined set of SLAs needed

SLAs are also helpfull for:• Measurement of capacity bottlenecks• the planning of capacity upgrades.

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Key terms in this chapter

• 24-bit• 64-bit• Address space• Capacity• Central storage• CP • Downtime• I/O• Interrupt• LPAR

• Mixed Workload

• Parallel Sysplex

• PR/SM

• PSW

• Real Storage

• SLA

• SVC

• The Bar

• The Line

• Virtual Storage

Introduction to the new mainframe: Large-Scale Commercial Computing © Copyright IBM Corp., 2006....

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