Podcast
Questions and Answers
What is a key consideration when deciding whether to buy or rent a car for short trips?
What is a key consideration when deciding whether to buy or rent a car for short trips?
Which of the following best explains the concept of the coefficient of variation (Cv)?
Which of the following best explains the concept of the coefficient of variation (Cv)?
What happens when demand is exponential in terms of provisioning?
What happens when demand is exponential in terms of provisioning?
What is one potential penalty of under-provisioning resources in an on-demand service model?
What is one potential penalty of under-provisioning resources in an on-demand service model?
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What characterizes the value proposition of on-demand services?
What characterizes the value proposition of on-demand services?
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In utility pricing models, what should be considered along with network costs?
In utility pricing models, what should be considered along with network costs?
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How do economies of scale impact service providers?
How do economies of scale impact service providers?
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What is the implication of having a flat demand curve for on-demand services?
What is the implication of having a flat demand curve for on-demand services?
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What does availability represent in cloud service metrics?
What does availability represent in cloud service metrics?
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Which metric measures how quickly the provider responds as resource loads change?
Which metric measures how quickly the provider responds as resource loads change?
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What does the service-level violation rate indicate?
What does the service-level violation rate indicate?
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Which metric describes the time from when a service is invoked to its completion?
Which metric describes the time from when a service is invoked to its completion?
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Which of the following is a key component of providing on-demand service value propositions?
Which of the following is a key component of providing on-demand service value propositions?
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What factor is considered when evaluating the impacts of latency on services?
What factor is considered when evaluating the impacts of latency on services?
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How is durability defined in the context of cloud services?
How is durability defined in the context of cloud services?
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Which option is NOT a benefit of economies of scale for service providers?
Which option is NOT a benefit of economies of scale for service providers?
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How does the addition of independent demands impact the coefficient of variation (CV)?
How does the addition of independent demands impact the coefficient of variation (CV)?
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What is the consequence of perfectly correlated demands in terms of variance and standard deviation?
What is the consequence of perfectly correlated demands in terms of variance and standard deviation?
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Which factor contributes significantly to latency in network services?
Which factor contributes significantly to latency in network services?
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How do economies of scale affect mid-size service providers as compared to large service providers?
How do economies of scale affect mid-size service providers as compared to large service providers?
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What is a crucial aspect of supporting a global user base through service architecture?
What is a crucial aspect of supporting a global user base through service architecture?
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What is the relationship between latency and routing algorithms in networks?
What is the relationship between latency and routing algorithms in networks?
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How do utility pricing models in cloud services differ from traditional pricing?
How do utility pricing models in cloud services differ from traditional pricing?
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What impact does location independence have on service architecture?
What impact does location independence have on service architecture?
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Study Notes
Multiplexing demand from multiple sources may reduce the coefficient of variation CV
- Adding n independent demands reduces the CV by n
- Aggregated demand:
- Variance: n.σ^2
- Mean: n.µ
- Aggregating 100 workloads brings the penalty to 10%
- CV represents the ratio of the standard deviation to the mean
But What about Workloads?
- Negative correlation demands: X and 1-X sum is random variable 1
- Perfectly correlated demands:
- Aggregated demand: n.X
- Variance: n^2σ^2(X)
- Mean: n.µ
- Standard deviation: n.σ(X)
- Coefficient of Variance remains constant
- Simultaneous peaks
Common Infrastructure in Real World
- Correlated demands: Private, mid-size and large-size providers can experience similar statistics of scale
- Independent demands: Midsize providers can achieve similar statistical economies to an infinitely large provider
- Available data on economy of scale for large providers is:
- Use the same COTS computers and components
- Locating near cheap power supplies
- Early entrant automation tools 3^rd^ parties take care of it
Value of Location Independence
- Latency is correlated with:
- Routing algorithms of routers and switches (second order effects)
- Speed of light in fiber: only 124 miles per millisecond
- Supporting a global user base requires a dispersed service architecture:
- Coordination, consistency, availability, partition-tolerance
- Investment implications
Value of Utility Pricing
- Economy of scale might not be very effective
- Cloud services don't need to be cheaper to be economical
- Consider a car:
- Buying or leasing can be more costly than renting if the car is only needed for a short period
Utility Pricing in Detail
- Baseline cost should be proportional to average demand
- When utility premium is less than the ratio of peak demand to average demand, utility pricing is beneficial
Utility Pricing in Real World
- Key factor is the ratio of peak to average demand
- Other costs to consider:
- Network cost (fixed costs and usage costs)
- Interoperability overhead
- Reliability, accessibility
Value of on-Demand Services
- On-demand services provide a trade-off between paying for unused resources and suffering the penalty of missing service delivery
Penalty Costs for Exponential Demand
- If demand is exponential (D(t)=e^t), any fixed provisioning interval will fall exponentially behind
Coefficient of Variation - Cv
- Statistical measure of the dispersion of data points in a data series around the mean
- The lower the ratio of standard deviation to mean, the better the risk-return tradeoff
Industry-defined KPIs
- Key performance indicators (KPIs) are used to monitor and audit cloud service providers
- Eliminates conflicts of interest if:
- Provider reports outage at its sole discretion
- Consumer is responsible for an outage
Metrics for Monitoring and Auditing
- Throughput - How quickly the service responds
- Availability - Represented as a percentage of uptime
- Reliability - How often the service is available
- Load balancing - When elasticity kicks in
- Durability - How likely the data is to be lost
- Elasticity - Ability for a resource to grow infinitely
- Linearity - How a system performs as the load increases
- Agility - How quickly the provider responds to scaling
- Automation - Percentage of requests handled without human intervention
- Customer service response times - Time it takes the provider to respond to a service request
- Service-level violation rate - Mean rate of SLA violation
- Transaction time - Time elapsed from service invocation to completion
- Resolution time - Time period between detection of a service problem and its resolution
SLA Requirements w.r.t.
- SLA requirements should align with the specific use case and performance objectives of the application or service
- Factors to consider:
- Service levels: Agreed upon performance targets and goals for key metrics. This often involves setting specific thresholds, targets, and acceptable ranges for metrics like availability, latency, throughput, and error rates.
- Monitoring and reporting: Regularly monitoring the service performance to ensure adherence to SLA requirements and providing reports to both provider and consumer on the current service status.
- Penalties and remedies: Defining specific actions and consequences for service level violations, including financial penalties, service credits, or other remediation options.
Assignment 1
- The cost to provision unit cloud resource for unit time is 0.9 units
- Possible mapping:
- Availability (A) = 1 -- (downtime/uptime)
- The text includes a calculation of the penalty cost based on the availability and other variables
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Description
This quiz delves into the implications of multiplexing demand from multiple sources on the coefficient of variation (CV). It covers concepts like independent and correlated demands, variance, mean, and the effects of workload aggregation. Test your understanding of statistical principles related to demand and workload management.
