Effective CISSP Questions

Your company initiates a business continuity program to support the continuous delivery of products and services. You’re in charge of the reliability and availability of the power system, including UPS and the power generator. Which of the following is the least concern for you? (Source: Wentz QOTD)
A. The default failure mode configuration
B. The mean time to repair (MTTR)
C. The mean time to failure (MTTF)
D. Service level agreement (SLA)

Kindly be reminded that the suggested answer is for your reference only. It doesn’t matter whether you have the right or wrong answer. What really matters is your reasoning process and justifications.

My suggested answer is A. The default failure mode configuration.

Maintenance for Availability

Default Failure Mode Configuration

  • A failure mode identifies a specific failure scenario and elaborates on its cause and effects.
  • Failure modes and effects analysis (FMEA) is a technique for analyzing failure and can be treated as a risk assessment approach.

After potential failure modes are identified, how should a system behave when a failure occurs? The default failure mode configuration can be fail-open (fail-safe) or fail-close (fail-secure).

You don’t have to worry about the default failure mode configuration of the power system because its objective is to keep the power provisioned constantly. For example, if a UPS is out of order, it cannot just shut down and stop the commercial power.

The Mean Time To Failure (MTTF)

Batteries of a UPS are consumables. They have a limited lifetime and should be replaced periodically. It’s common for organizations to suffer the disruptive incident because of the malfunction batteries of the UPS.

The Mean Time to Repair (MTTR)

The power generator and other fixed assets are typically repairable. It’s not feasible to replace those fixed assets with new ones whenever they are broken. Typically, we fix them and it takes time. It’s crucial to know the MTTR of the power system to maintain business continuity.

Service Level Agreement (SLA)

Service level agreement (SLA) can be an internal agreement with your internal “customers” or departments. For sure, it applies to the maintenance service provider of the power system.


貴公司啟動業務連續性計畫以支持產品和服務的持續交付。 您負責電源系統(包括UPS和發電機)的可靠性和可用性。 以下哪項是您最不用擔心的問題? (來源:Wentz QOTD)
A. 默認故障模式組態 (Failure mode)
B. 平均維修時間 (MTTR)
C. 平均故障時間 (MTTF)
D. 服務水平協議 (SLA)


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