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COMP9334: Capacity Planning for Computer Systems and Networks

COMP9334: Capacity Planning for Computer Systems and Networks. Week 1: Introduction Lecturer: Dr Bruce Howarth. Introduction. This subject Why performance is important Overview of capacity planning Review: Web protocols. What is capacity planning?. Determine desired service levels

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COMP9334: Capacity Planning for Computer Systems and Networks

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  1. COMP9334: Capacity Planningfor Computer Systems and Networks Week 1: Introduction Lecturer: Dr Bruce Howarth

  2. Introduction • This subject • Why performance is important • Overview of capacity planning • Review: Web protocols

  3. What is capacity planning? • Determine desired service levels • Measure actual workload • Measure actual performance • Tune as necessary • Create performance models • Predict workload growth • Predict capacity required to maintain service levels

  4. Comments • All these steps are hard to do • All have serious costs • Tools, time, gaining expertise • Lots of politics and negotiation • Lots of compromises and tradeoffs

  5. Related activities • Software performance engineering • Designing performance into applications • Better than designing it out • Technology assessment • Examining new and coming technologies • Consider how they affect ability to deliver required services

  6. Why worry about performance? • Slow systems lose money • Employees waste time waiting • Customers will not buy if website too slow • They’ll go elsewhere • Performance is hard to control • Especially in Web applications • Many delays are outside your organization

  7. Why worry (cont.)? • Systems are complex, hard to understand • N-tier systems • Multiple servers networked together • Complex storage subsystems: • RAID, SANs, etc • Can be hard to identify cause of performance problems

  8. Why worry (cont.)? • “Throwing hardware” may not work • Especially if it’s the wrong hardware • E.g., a faster CPU won’t solve a disk problem • Or the software uses slow algorithms • E.g., linear search vs index • Extra hardware can have hidden costs • Software license fees, power, cabling ...

  9. Performance Examples • Menascé gives typical cases in Ch. 1 • Lost revenue from an overloaded Web server • Sizing a distributed client-server system • Uses the tools described later • The problems are quite realistic

  10. System Architectures - review • We assume you know about: • Basic computer organization • Memory hierarchy, virtual memory • Process scheduling: • Round robin, context switch • Process priority structures • Basic concepts of client-server systems • Some of this material is reviewed in Menascé

  11. Communications basics - review • We assume you know about: • Basic data transfer • LANs and WANs • Protocol concepts • TCP/IP, HTTP, and similar • Much of this material is reviewed in Menascé

  12. Not in Menascé • Storage area networks • Switched ethernet • IEEE 802.11 (wireless ethernet) • (But same models as basic IEEE802) • What else?

  13. Protocols and performance • Menascé describes how TCP takes a while to initiate a connection • Also how HTTP adds overhead to exchanges • You need to understand how these work and the magnitudes of the effects

  14. Web service protocols • Menascé introduces the likely future of Web services: • SOAP - simple object access protocol • WSDL - web services description language • UDDI - universal description, discovery and integration

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