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Deco1

P.1~11

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Deco1

  1. 1. The Datacenter as a Computer Introduction 2009/12/06 id:daisukebe
  2. 2. PC to Internet • computing and storage are moving from clients to Internet service • email, photo, video, and office application... • allow user to run at a low cost
  3. 3. Toward WSC • the massive scale of their software infrastructure, data repositories, and hardware platform • a departure from a single machine • the program is an Internet service
  4. 4. Overview of WSC • run a smaller number of very large applications(or Internet services) • must be designed to gracefully tolerate large numbers of component faults • building and operating a large computing platform is expensive
  5. 5. Cost Efficiency • building and operating a large computing platform is expensive • cost efficiency must be defined broadly to account for all the components of cost
  6. 6. eg. • Web search system is driven by the following: 1. Increasing popularity means higher request loads 2. 1,000,000p/day means building a index 3. most substantial improvements demand additional computing resources
  7. 7. What’s WSC? • the machine, the computer, is the large cluster or aggregation of servers itself and a single computing unit • WSCs have an additional layer of complexity beyond systems consisting of individual servers or small groups of server • introduce new challenge to programmer productivity, a challenge perhaps greater than programming multicore systems
  8. 8. Why WSC? • a rack with 40 servers, each with four 8- core dual-threaded CPUs, would contain more than two thousand H/W threads • many org. will soon be able to afford similarly sized computers at a much lower cost • this experience will be useful for ubiquitous next-generation machines
  9. 9. Architecture Typical elements in warehouse-scale systems: 1U server(left), 7` rack with Ethernet switch(middle), and diagram of a small cluster with a cluster-level Ethernet switch/router(right)
  10. 10. Architecture -Storage • connecting directly to each individual server(managed by GFS) or being part of NAS? • NAS provides extra reliability • GFS implement replication across different machines • WSCs deploy desktop-class disk drives instead of enterprise-grade disks
  11. 11. Architecture -Networking Fabric • trading-off between speed, scale, and cost • a switch that has 10 times the bi-section bandwidth costs about 100 times as much • intra rack connectivity is often cheaper than inter rack connectivity
  12. 12. Architecture ~Storage Hierarchy • DRAM and disk resources within the rack are accessible through the first-level rack switches • all resources in the racks are accessible via the cluster-level switch
  13. 13. Latency, Bandwidth, Capacity • the graph shows the latency, bandwidth, and capacity of each resource pool
  14. 14. Latency, Bandwidth, Capacity • these discrepancies are much larger than those seen on a single machine • a key challenge for architects of WSCs is to smooth out these discrepancies in a cost-efficient manner • a key challenge for software architects is to build cluster infrastructure and services that hide most of this complexity from application developers
  15. 15. Power Usage • energy-related costs have become an important component of the total cost of ownership • CPUs can no longer be the sole focus of energy efficiency
  16. 16. Handling Failures • the sheer scale of WSCs requires that Internet services software tolerate relatively high component fault rates • an application running across thousands of machines may need to react to failure conditions on an hourly basis

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