exam_2020

Question 1

Q1.A The CAP principle makes a statement about 3 properties. Give the definition of each property

Answer 1

C = Consistency
A = Availability
P = Partition Resistence

C = Every read receives the most recent write or an error
A = Every request receives a (non-error) response, without the guarantee that it contains the most recent write
P = The system continues to operate despite an arbitrary number of messages being dropped (or delayed) by the network between nodes

Question 2

Q1.B Explain why you cannot have all 3 CAP properties at the same time

Answer 2

When a network partition happens, it must be decided whether to:

• Cancel the operation and thus decrease the availability but ensure consistency or;
• Proceed with the operation and thus provide availability but risk consistency

Question 3

Give another explanation for unable to have all 3 cap properties

Answer 3

Partition tolerance is must because it saves the data from getting completely lost due to Network/Node failure.

Therefore, the choice is between consistency and availability.

If you try to achieve consistency (all nodes give same and most recent write data) we have to sacrifice availability because it takes time to synchronise data to every replica of the node. While it’s synchronising, it may not be able to respond to requests of information retrieval thus hindering availability.

If you try to achieve availability (every non-failing node have to return a reasonable response, in reasonable time) we have to sacrifice consistency because while system is updating/synchronising all replicas/nodes with latest written data to make system consistent, and if meanwhile it got an request, it have to respond to make system available and in that case it might respond with an un-updated data because all nodes haven’t been updated and it have to reply in reasonable time

Question 4

What are the six characteristics of containers?

Answer 4

1. Namespaces
2. Resource Control
3. Security
4. Images
5. Open Standards
6. Management

Question 5

What are namespaces in containers?

Answer 5

Provide containers a way to identify and personalise their own space

Question 6

Resource control in containers?

Answer 6

You want one piggie flushing the toilet not to raise water temperature in another.

Cgroups are used to manage container resource control. If you have written poorly-written cgroup configuration, you’ll run into problems with resources

Question 7

Security in containers?

Answer 7

SELinux, security analysis tools and access to Red Hat security experts

Question 8

Images in containers

Answer 8

You can make them from scratch but it’s better to use the red hat registry to have it fully furnished

Question 9

Community standards in containers?

Answer 9

This is about standardisation and consistency. This improves application portability and allows you to deploy container-based applications anywhere

Question 10

Management in containers?

Answer 10

Management and upkeep is important with apartments - especially as you scale up. CloudForms help streamline node and container creation, deployment, workflows and management