Service Level Agreements (SLAs)

Question 1

Service Level Agreement

Answer 1

• A document that describes quality-of-service features, behaviors, and limitations of a service.
• Considered a human-readable part of a service contract that extends the technical service contract
• Because cloud environments intentionally hide back-end implementation details about cloud services, the guarantees expressed in SLAs become very important to cloud consumers

Question 2

Availability

Answer 2

• The probability value is generally expressed with a percentage representing the amount of time that the IT resource is accessible during a given period
• 100 - ((time unavailable)/(total time)*100)
• The availability value guaranteed in the SLA is based on assumptions regarding future downtimes
• 100 - (((prob of downtime * actual estimated downtime)/total time) * 100)

Question 3

Reliability

Answer 3

• Represents the probability that an IT resource performs its intended functions without failure under predefined conditions
• (successful executions / total execution attempts) *100
• Closely related to availability because, in order to be reliable, the IT resource needs to be available.

Question 4

Performance

Answer 4

• The maximum performance of an IT resource represents the capacity up to which the IT resource is able to perform its functions
• the determination of this capacity (the performance rating) of a given IT resource depends on its type and purpose

Question 5

Redundancy / Resiliency

Answer 5

• It is important to note that the availability, reliability and performance of an IT resource can be made more resilient by providing redundant implementations of the IT resource.
• Performance and response times can be improved by incorporating load balancing logic that can defer requests to redundant implementations, as required