AWS 9.7 reliability and availability

Question 1

reliability

Answer 1

Reliability is the ability of a system to function correctly for a specified period. All components (hardware, software, network) must work together — like a car: if one component fails (e.g., ignition), the system fails.

Question 2

MTBF and MTTR

Answer 2

• MTBF (Mean Time Between Failures): Average time a system runs before failing • MTTR (Mean Time To Repair): Time taken to recover from failure Higher MTBF + Lower MTTR = Better reliability

Question 3

MTBF and MTTR calculation

Answer 3

MTBF = 96 hours MTTR = 72 hours Indicates poor reliability due to long recovery time.

Question 4

availability

Answer 4

Availability = percentage of time system is operational Measured as uptime over total time (e.g., 99.9% availability).

Question 5

five nines availability

Answer 5

99.999% availability Means extremely low downtime (~minutes per year), used for critical systems.

Question 6

high availability

Answer 6

High availability Achieved using: • Redundancy • Failover systems • Distributed resources

Question 7

high availability with downtime

Answer 7

Availability cannot be perfect — influenced by: • Fault tolerance (redundancy) • Scalability (handling load) • Recoverability (restoring quickly after failure)