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Determining which storage mechanism to use should be based on the needs of the organization, the availability of storage facilities, and the budget available. Most offsite storage facilities charge based on the amount of space you require and the frequency of access you need to the stored information.

Crafting a Disaster-Recovery Plan

A disaster-recovery plan, or scheme, helps an organization respond effectively when a disaster occurs. Disasters may include system failure, network failure, infrastructure failure, and natural disaster. The primary emphasis of such a plan is reestablishing services and minimizing losses.

In a smaller organization, a disaster-recovery plan may be relatively simple and straightforward. In a larger organization, it may involve multiple facilities, corporate strategic plans, and entire departments. In either case, the purpose is to develop the means and methods to restore services as quickly as possible and to protect the organization from unacceptable losses in the event of a disaster.

A major component of a disaster-recovery plan involves the access and storage of information. Your backup plan for data is an integral part of this process. The following sections address backup plan issues and backup types. They also discuss developing a backup plan, recovering a system, and using alternative sites. These are key components of a disaster-recovery plan: They form the heart of how an organization will respond when a critical failure or disaster occurs.

Understanding Backup Plan Issues

When an organization develops a backup plan for information, it must be clear about the value of the information. A backup plan identifies which information is to be stored, how it will be stored, and for what duration it will be stored. You must look at the relative value of the information you retain. To some extent, the types of systems you use and the applications you support dictate the structure of your plan.

Let’s look at those different systems and applications:

Database systems Most modern database systems provide the ability to globally back up data or certain sections of the database without difficulty. Larger-scale database systems also provide transaction auditing and data-recovery capabilities.

For example, you can configure your database to record in a separate file each addition, update, deletion, or change of information that occurs. These transaction or audit files can be stored directly on archival media, such as magnetic tape cartridges. In the event of a system outage or data loss, the audit file can be used to roll back the database and update it to the last transactions made.

Figure 8.3 illustrates the auditing process in further detail. In this situation, the audit file is directly written to a DAT tape that is used to store a record of changes. If an outage occurs, the audit or transaction files can be rolled forward to bring the database back to its most current state. This recovery process brings the database current to within the last few transactions. Although it doesn’t ensure that all the transactions that were in process will be recovered, it will reduce potential losses to the few that were in process when the system failed.

FIGURE 8.3 Database transaction auditing process

Most database systems contain large files that have only a relatively few records updated in relation to the number of records stored. A large customer database may store millions of records—however, only a few hundred may be undergoing modification at any given time.

User files Word-processing documents, spreadsheets, and other user files are extremely valuable to an organization. Fortunately, although the number of files that people retain is usually large, the number of files that change after initial creation is relatively small. By doing a regular backup on user systems, you can protect these documents and ensure that they’re recoverable in the event of a loss. In a large organization, backing up user files can be an enormous task. Fortunately,