Cloud Computing

Question 1

Why use cloud computing?

Answer 1

It offers expertise and economies of scale that small organisations could not hope to match

Question 2

What are the 5 things that make the cloud successful?

Answer 2

1. Broad Network Access
2. On-Demand, Self-Service
3. Measured Service
4. Rapid Elasticity
5. Resource Pooling

Question 3

What does Broad Network Access mean?

Answer 3

The cloud is widely available over standard networks

Question 4

What does On-Demand Self-Service mean?

Answer 4

Customers can easily acquire VM/cloud access, usually on a ‘drug-dealer’ pricing model

Question 5

What is the drug dealer pricing model?

Answer 5

• A company offers a small amount of their product for free
• Expect that they will come back and purchase more in the future

Question 6

What does Measured Service mean?

Answer 6

The provider monitors usage for optimisation and bills exactly for usage

Question 7

What does Rapid Elasticity mean?

Answer 7

Customers can easily add or release VMs in response to a changing demand

Question 8

What does Resource Pooling mean?

Answer 8

Providers assign multiple VMs to physical ones, achieving multitenancy (which splits resources between VMs fairly)

Question 9

What are the two phases of cloud computing? Which is the “wrong” method?

Answer 9

1. Serverful
2. Serverless

David thinks the Serverful method is the “wrong” one

Question 10

What are some serverful models?

Answer 10

1. Infrastructure-as-a-Service (IaaS)
2. Platform-as-a-Service (PaaS)
3. Software-as-a-Service (SaaS)

Question 11

What is Infrastructure-as-a-Service?

Answer 11

A serverful model which gives access to bare (empty) servers

Question 12

What is Platform-as-a-Service?

Answer 12

A serverful model which gives access to servers with operating systems and tools

Question 13

What is Software-as-a-Service?

Answer 13

A serverful model which gives access to applications (on a subscription)

Question 14

What is multitenancy? How is it implemented?

Answer 14

• A single instance of an application serves multiple tenants
• Implemented using virtualisation using:
  1. many VMs run on a physical machine with a hypervisor
  2. many containers run on a physical machine

Question 15

What are the ways to implement microservices in the serverful model?

Answer 15

1. Run a single microservice on a single VM
2. Run a single microservice in a single container

Question 16

What are some serverless models?

Answer 16

1. Backend-as-a-Service (BaaS)
2. Function-as-a-Service (FaaS)

Question 17

What is Backend-as-a-Service?

Answer 17

A serverless model which gives access to backend services, so an organisation only has to maintain front-end

Question 18

What is Function-as-a-Service?

Answer 18

A serverless model which runs custom code in response to a request

Question 19

How is a serverless model implemented?

Answer 19

• Typically make use of “hidden” containers
• Does not mean that servers are not used, just that they do not concern the customers

Question 20

What is the cost model for the serverless model?

Answer 20

It charges customers for execution time, on a pay-as-you-go basis

Paying for a taxi analogy

Question 21

What are the ways to implement microservices in serverless?

Answer 21

1. Mapping a single microservice to a single function instance
2. Mapping a single microservice to multiple functions

Question 22

Do you have to choose between speed and stability?

Answer 22

No: moving fast means breaking things more but fixing things faster