Introduction to the new mainframe Large-Scale Commercial Computing

Introduction to the new mainframe: Large-Scale Commercial Computing Chapter 2: Capacity © Copyright IBM Corp. , 2006. All rights reserved.

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 © Copyright IBM Corp. , 2006. All rights reserved. 2

Introduction to the new mainframe Definition of 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 © Copyright IBM Corp. , 2006. All rights reserved. 3

Introduction to the new mainframe Elements required for capacity (1/2) Any computer system, from a single-user PC to a multithousand 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 © Copyright IBM Corp. , 2006. All rights reserved. 4

Introduction to the new mainframe Elements required for capacity (2/2) The relevant components to perform these steps and therefore for capacity estimation & planning are: Ø Processors Ø Central storage Ø Access input/output storage (for example disk or tape) Ø Also the network to these devices has to be considered © Copyright IBM Corp. , 2006. All rights reserved. 5

Introduction to the new mainframe Many servers Few Servers Many servers : Ø Data retention ? Ø Locking across servers ? Ø Connectivity ? Few servers (IBM System z): Ø Large volumes of data: best in 1 place Ø No rewitting needed of applications Ø 1 total system © Copyright IBM Corp. , 2006. All rights reserved. 6

Introduction to the new mainframe 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. © Copyright IBM Corp. , 2006. All rights reserved. 7

Introduction to the new mainframe 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. © Copyright IBM Corp. , 2006. All rights reserved. 8

Introduction to the new mainframe Managing the system to the SLA Ø Managing CPU Ø Managing Disk Ø Storage concepts (the address space) -> see next slide Ø Real storage mangement © Copyright IBM Corp. , 2006. All rights reserved. 9

Introduction to the new mainframe Address space Ø The „Line“ 24 Bit systems Ø The „Bar“ 31 Bit systems © Copyright IBM Corp. , 2006. All rights reserved. 10

Introduction to the new mainframe Architecture, running work & capacity Ø Program Status Word (PSW) Ø Interrupts • • • Ø Ø 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 © Copyright IBM Corp. , 2006. All rights reserved. 11

Introduction to the new mainframe Several servers on 1 physical machine Ø LPAR Ø Planning for downtime • Software • Hardware © Copyright IBM Corp. , 2006. All rights reserved. 12

Introduction to the new mainframe IBM System z – Parallel Sysplex Coupling Facility Z 9 EC Z 9 BC Parallel Sysplex SYSPLEX Timer Z 9 EC ESCON/FICON Z 9 BC Shared Data © Copyright IBM Corp. , 2006. All rights reserved. 13

Introduction to the new mainframe Measurements Ø Central Processor usage Ø Central storage usage Ø Access to disk storage © Copyright IBM Corp. , 2006. All rights reserved. 14

Introduction to the new mainframe Summary Capacity Ø Complex when you are : • In a mixed workload • On a large-scale commercial environment Ø Different workloads different requirements well defined set of SLAs needed Ø SLAs are also helpfull for: • Measurement of capacity bottlenecks • the planning of capacity upgrades. © Copyright IBM Corp. , 2006. All rights reserved. 15

Introduction to the new mainframe 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 © Copyright IBM Corp. , 2006. All rights reserved. 16