Information Storage and Management: Storing, Managing, and Protecting Digital Information in Classic, Virtualized, and Cloud Environments, Second Edition

Appendix D

Information Availability Exercises

Exercise 1

A system has three components and requires all three components to be operational 24 hours, Monday through Friday. Failure of component 1 occurs as follows:

• Monday = No failure.
• Tuesday = 5 a.m. to 7 a.m.
• Wednesday = No failure.
• Thursday = 4 p.m. to 8 p.m.
• Friday = 8 a.m. to 11 a.m.

Calculate the MTBF and MTTR of component 1.

Solution

The formula for MTBF is

Therefore,

The formula for MTTR is

Therefore,

So,

Exercise 2

A system has three components and requires all three components to be operational during 8 a.m. through 5 p.m. business hours, Monday through Friday. Failure of component 2 occurs as follows:

• Monday = 8 a.m. to 11 a.m.
• Tuesday = No failure.
• Wednesday = 4 p.m. to 7 p.m.
• Thursday = 5 p.m. to 8 p.m.
• Friday = 1 p.m. to 2 p.m.

Calculate the availability of component 2.

Solution

Operational hours are 8 a.m. through ...