Download - Lecture 2: Introduction to Cloud Computing
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Lecture 2: Introduction to Cloud Computing
Xiaowei Yang (Duke University)
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Roadmap• What is Cloud Computing?
• Why now, not then?
• Classes of Cloud Computing
• Cloud Computing Economics: why does it make sense?
• Obstacles and (research) opportunities
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What is cloud computing• Applications run on clouds (Software
as a Service)• Hardware and system software in the
datacenters that provide the services– An old concept: computing as a utility• No need to purchase your hardware• Pay-as-you-go
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Cloud Computing = SaaS + UtilityComputing – PrivateClouds
• Private– A business’s internal datacenters– No public access– Name a few companies that own private
clouds• Public– Pay-as-you-go public services– Name a few public cloud providers
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Who’s whom
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Is Cloud Computing Win-Win?
• SaaS advantages to providers– Simple management and maintanence– Centralized control over versioning
• SaaS Advantages to users– Always on service– Easy data sharing and collaboration– Robust data storage– Simple management–…
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• Advantages of utility computing to users– On demand scaling (elasticity)– No up-front commitment– Pay-as-you-go reduces provisioning risk
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Examples–When Animoto made its service available
via Facebook, it experienced a demand surge that resulted in growing from 50 servers to 3500 servers in three days. … After the peak subsided, traffic fell to a level that was well below the peak.
• With traditional computing buy servers idle servers• With cloud computing pay during peaks
release afterwards
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Incentives for cloud providers
1. Making money– Wholesale (10,000s) at a larger scale is 5-7
times cheaper than retail at a medium size (100s - 1000s)
– Resource multiplexing2. Leveraging existing investment– Companies may already build private clouds
for other businesses3. Defend a franchise– Migrating existing customers to a cloud
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4. Attacking an incumbent– Google vs MS
5. Leveraging customer relationships– E.g. IBM– Preserving relationships by offering a
branded cloud computing service6. Becoming a platform– More customers more $$
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Why now?• Two enablers:– New business model: pay-as-you-go with
no contract• Intel Computing Service in 2000-2001
required a contract and longer-term use and failed• Customers do not like commitment
– New applications• Mobile + cloud• Parallel batch processing: tons of data today• Analytics• Compute-intensive desktop applications
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Classes of Utility Computing• Infrastructure as a service (IaaS)– Thin API, close to bare metal – Virtual machines with customized guest OSes– Applications run on virtual machines using OS
APIs– E.g. Amazon EC2
• Platform as a service (PaaS)– Sandbox environment with specific platform APIs– E.g. Google AppEngine
• A mixture of both– Microsoft Azure
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Economic benefits• Elasticity– Peak demand: 500 servers– Average demand: 300 servers
– Q: when does it make sense to use a cloud?
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Reducing underprovisioning risk
• Poor performance turns customers away
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Real world examples• Target uses AWS• Other retailers use it during holiday
seasons
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Rule of Thumb• UserHourscloud x (revenue – Costcloud)
>= UserHoursdatacenter * (revenue – Costdatacenter/Utilization)
• Why Costdatacenter/Utilization?• Do UserHourscloud ==
UserHoursdatacenter
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Comparing costs
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When not to use a cloud?• Utilization = 100%
• Shipping large amount of data
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Obstacles and Opportunities• Availability– Single point of failure• Mega-Cloud to improve reliability• Elasticity to defend against DoS attacks
– Ex. 500,000 bots at $0.03 per bot, 1GB/s attack traffic
– Victim: $360 per hour in bandwidth and $100 of computation, (500 bots per instance)
– Attack must last long (>32 hours) – Make bots detectable
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Obstacles and Opportunities• Data Lock-in– Not a pure technical problem–Marketing strategy– Standardarization
• Data confidentiality and auditability– Technical challenge– Encryption would help
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Obstacles and Opportunities• Data transfer bottlenecks– Need creative solutions• FedEx• Keep data local to a cloud• Cheap long haul bandwidth by reducing high-
end router cost– 2/3 of bandwidth cost is from routers
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Obstacles and Opportunities
• Performance variation caused by I/O sharing–More research
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Obstacles and opportunities• Scalable storage– Research to build scalable storage systems
• Bugs– Debuggers, tracers
• Scaling quickly– Research
• Reputation fate sharing– Spammers used EC2– All services sharing their IP addresses got
blacklisted– Research
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Obstacles and opportunities• Software licensing– Not pure technical challenges• Commercial software’s licensing model not
good for utility computing– One time purchase vs pay-as-you-go
– Opportunities• New licensing models• New sales models• Open source software!
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Summary• What is cloud computing– SaaS + Utility Computing – Private Cloud
• Enablers– Business models– New applications
• Advantages• Economic benefits• Challenges and opportunities– Technical– Non-technical