If you’re planning on taking the Security+ exam, you should have a basic understanding of adding redundancy as one of the risk management best practices such as disk, server, site and power redundancies.
For example, can you answer this question?
Q. You are a technician at a small organization. You need to add fault-tolerance capabilities within the business to increase the availability of data. However, you need to keep costs as low as possible. Which of the following is the BEST choice to meet these needs?
A. Failover cluster
B. RAID-6
C. Backups
D. UPS
More, do you know why the correct answer is correct and the incorrect answers are incorrect? The answer and explanation is available at the end of this post.
Disk Redundancies
Any system has four primary resources: processor, memory, disk, and the network interface. Of these, the disk is the slowest and most susceptible to failure. Because of this, administrators often upgrade disk subsystems to improve their performance and redundancy.
Redundant array of inexpensive disks (RAID) subsystems provide fault tolerance for disks and increase the system availability. Even if a disk fails, most RAID subsystems can tolerate the failure and the system will continue to operate. RAID systems are becoming much more affordable as the price of drives steadily falls and disk capacity steadily increases.
Some common types of RAID are summarized in this blog post.
Software Versus Hardware RAID
Hardware RAID configurations are significantly better than software RAID. In hardware RAID, dedicated hardware manages the disks in the RAID, removing the load from the operating system. In contrast, the operating system manages the disks in the RAID array in software RAID. Hardware RAID systems provide better overall performance and often include extra features.
For example, a hardware RAID may include six physical disks using four in an active RAID-6 configuration and two as online spares. If one of the active disks in the RAID-6 fails, the RAID will continue to operate because a RAID-6 can tolerate the failure.
However, a hardware RAID can logically take the failed disk out of the configuration, add one of the online spares into the configuration, and rebuild the array. All of this happens without any administrator intervention. Hardware RAID systems are often hot swappable, allowing administrators to swap out the failed drive without powering the system down.
Power Redundancies
Power is a critical utility to consider when reviewing redundancies. For mission-critical systems, you can use uninterruptible power supplies and generators to provide both fault tolerance and high availability.
UPS
An uninterruptible power supply (UPS) is a battery or bank of batteries used as a backup in case of primary power failure. The UPS plugs into the wall and receives power from a commercial power source. The commercial power keeps the batteries charged and electronics within the UPS system provide power to external systems.
If commercial power fails, the UPS continues to provide power without any interruption. One of the added benefits of a UPS system is that it can protect against power fluctuations. Even if commercial power has momentary fluctuations, external systems aren’t affected because they receive their power directly from the UPS.
The 601 Version of the Study Guide
The CompTIA Security+: Get Certified Get Ahead: SY0-601 Study GuideEach of the eleven chapters presents topics in an easy to understand manner and includes real-world examples of security principles in action.
You’ll understand the important and relevant security topics for the Security+ exam, without being overloaded with unnecessary details. Additionally, each chapter includes a comprehensive review section to help you focus on what’s important.
Over 300 realistic practice test questions with in-depth explanations will help you test your comprehension and readiness for the exam. The book includes:
- A 75 question pre-test
- A 75 question post-test
- Practice test questions at the end of every chapter.
Each practice test question includes a detailed explanation to help you understand the content and the reasoning behind the question. You’ll be ready to take and pass the exam the first time you take it.
If you plan to pursue any of the advanced security certifications, this guide will also help you lay a solid foundation of security knowledge. Learn this material, and you’ll be a step ahead for other exams. This SY0-601 study guide is for any IT or security professional interested in advancing in their field, and a must-read for anyone striving to master the basics of IT security.
Common UPS systems provide power for 10 to 15 minutes after a power outage. They aren’t meant to provide longer-term power. Instead, the goal is to provide power until one of the following events occurs:
- The supported system has enough time to shut down. For example, a 10-minute UPS may send a shutdown signal to a system after power has been lost for 5 minutes. The system now has 5 minutes to perform an orderly shutdown.
- Generators have enough time to power up and stabilize. Both UPSs and generators support critical systems. The UPS provides short-term power, and the generator provides long-term power.
- Commercial power returns. A UPS provides fault tolerance for short outages and momentary power fluctuations. When commercial power returns, it recharges the batteries to get them back to full potential.
Generators
Many organizations use generators for critical systems that need long-term power. It isn’t feasible to keep the generators running all the time due to fuel costs. Instead, they are started when power fails. Because it takes time for a generator to rev up to full power and stabilize, it cannot provide AC power immediately. A UPS powers critical systems until the generators stabilize.
In some cases, a generator automatically turns on when it detects power is lost and automatically switches over to generator power after the generator stabilizes. In other cases, technicians power up the generators manually, and manually switch over to generator power when the generators stabilize.
Remember this
An uninterruptible power supply (UPS) provides fault tolerance for power and can protect against power fluctuations. A UPS provides short-term power. Generators provide long-term power in extended outages.
Q. You are a technician at a small organization. You need to add fault-tolerance capabilities within the business to increase the availability of data. However, you need to keep costs as low as possible. Which of the following is the BEST choice to meet these needs?
A. Failover cluster
B. RAID-6
C. Backups
D. UPS
Answer is B. A redundant array of inexpensive disks 6 (RAID-6) subsystem provides fault tolerance for disks, and increases data availability.
A failover cluster provides fault tolerance for servers and can increase data availability but is significantly more expensive than a RAID subsystem.
Backups help ensure data availability, but they do not help with fault tolerance.
An uninterruptible power supply (UPS) provides fault tolerance for power, but not necessarily for data.
Here’s a helpful blog post about Adding Redundancy.
