CompTIA Security_ Deluxe Study Guide_ SY0-201 - Emmett Dulaney [205]
Scenario 2 You’re the administrator for a small educational company that delivers certification exams locally. The exams are downloaded the night before and delivered throughout the day as students—who have registered over the Internet—arrive. You show up at 8:00 a.m. on Friday, knowing that there are more than 20 exams to be administered that were downloaded Thursday night. What you find, however, is that someone has broken into the testing room and trashed all the workstations and monitors. Some of those coming to take the exams are driving from far away. How will you approach the situation?
Scenario 3 You’re the database administrator for a large grocery chain. When you leave on Wednesday, there are no problems. When you arrive on Thursday—the day a new sale starts—you learn that the DSL lines are down. They went down before the local stores could download the new prices. All scanned goods will ring up at the price they were last week (either sale or regular) and not at current prices. The provider says it’s working on the DSL problem but can’t estimate how long repairs will take. How do you approach the problem?
Just like in the real world, there are no right or wrong answers for these scenarios. However, they all represent situations that have happened and that administrators planned for ahead of time.
There are several ways to accomplish this, including implementing redundant technology, fault-tolerant systems, and backup communications channels. A truly redundant system won’t utilize just one of these methods but rather some aspect of all of them. The following sections address these topics in more detail.
Redundancy
Redundancy refers to systems that are either duplicated or that fail over to other systems in the event of a malfunction. Fail-over refers to the process of reconstructing a system or switching over to other systems when a failure is detected. In the case of a server, the server switches to a redundant server when a fault is detected. This allows service to continue uninterrupted until the primary server can be restored. In the case of a network, processing switches to another network path in the event of a network failure in the primary path.
Fail-over systems can be very expensive to implement. In a large corporate network or e-commerce environment, a fail-over might entail switching all processing to a remote location until your primary facility is operational. The primary site and the remote site would synchronize data to ensure that information is as up-to-date as possible.
Many newer operating systems, such as Linux, Windows Server 2008, and Novell Open Enterprise Server, are capable of clustering to provide fail-over capabilities. Clustering involves multiple systems connected together cooperatively and networked in such a way that if any of the systems fail, the other systems take up the slack and continue to operate. The overall capability of the server cluster may decrease, but the network or service will remain operational.
To appreciate the beauty of clustering, contemplate the fact that it is this technology upon which Google is built. Clustering not only allows the company to have redundancy, it also offers it the ability to scale as demand increases.
Figure 8.1 shows the clustering process in a network. In this cluster, each system has its own data storage and data-processing capabilities. The system that is connected to the network has the additional task of managing communication between the