If you’re planning on taking the Security+ exam, you should have a good understanding of failover clusters and how they provide high availability for a service offered by a server.
For example, can you answer this question?
Q. Your organization hosts a web site with a back-end database server. During a recent power outage, the server crashed, resulting in a significant amount of lost data. Which of the following can your organization implement to prevent this loss from occurring again?
A. Redundancy
B. Disaster recovery procedures
C. Warm site
D. Higher RTO
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.
Server Redundancy
Some services require a high level of availability and it’s possible to achieve 99.999 percent uptime, commonly called five nines. It equates to less than 6 minutes of downtime a year: 60 minutes × 24 hours × 365 days × .00001 = 5.256 minutes. Failover clusters are a key component used to achieve five nines.
Although five nines is achievable, it’s expensive. However, if the potential cost of an outage is high, the high cost of the redundant technologies is justified. For example, some web sites generate a significant amount of revenue, and every minute a web site is unavailable represents lost money. High-capacity failover clusters ensure the service is always available even if a server fails.
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.
Failover Clusters for High Availability
The primary purpose of a failover cluster is to provide high availability for a service offered by a server. Failover clusters use two or more servers in a cluster configuration, and the servers are referred to as nodes. At least one server or node is active and at least one is inactive. If an active node fails, the inactive node can take over the load without interruption to clients.
Consider the following figure, which shows a two-node failover cluster. Both nodes are individual servers, and they both have access to external data storage used by the active server. Additionally, the two nodes have a monitoring connection to each other used to check the health or heartbeat of each other.
Failover cluster
Imagine that Node 1 is the active node. When any of the clients connect, the cluster software (installed on both nodes) ensures that the clients connect to the active node. If Node 1 fails, Node 2 senses the failure through the heartbeat connection and configures itself as the active node. Because both nodes have access to the shared storage, there is no loss of data for the client. Clients may notice a momentary hiccup or pause, but the service continues.
You might notice that the shared storage in the figure represents a single point of failure. It’s not uncommon for this to be a robust hardware RAID-6. This ensures that even if two hard drives in the shared storage fails, the service will continue. Additionally, if both nodes are plugged into the same power grid, the power represents a single point of failure. They can each be protected with a separate uninterruptible power supply (UPS), and use a separate power grid.
Cluster configurations can include many more nodes than just two. However, nodes need to have close to identical hardware and are often quite expensive, but if a company truly needs to achieve 99.999 percent uptime, it’s worth the expense.
Q. Your organization hosts a web site with a back-end database server. During a recent power outage, the server crashed, resulting in a significant amount of lost data. Which of the following can your organization implement to prevent this loss from occurring again?
A. Redundancy
B. Disaster recovery procedures
C. Warm site
D. Higher RTO
Answer is A. Server redundancy solutions such as a failover cluster would prevent this type of loss. Additionally, a power redundancy solution such as an uninterruptible power supply (UPS) would prevent this.
Disaster recovery procedures help restore the systems after a disaster, but they wouldn’t prevent the incident.
A warm site is as an alternate site, but it wouldn’t prevent data loss.
The recovery time objective (RTO) identifies the time period when you plan to restore a system after an outage, but it doesn’t prevent a loss.
