Disaster Recovery Planning

Disaster recovery planning is an important part of any organization's business operations. Disaster recovery planning is not just for servers, but is for the entire company. Not only does the organization need a plan to recover the server, but also the network, including helping the users connect if physical access to an office is unavailable.

Elements of a Disaster

Disasters come in many shapes and forms. This chapter covers backing up Windows Server 2003, but it would not be complete unless we at least outlined all the different areas that should be investigated and addressed when tasked with creating a disaster recovery plan for a computer and networking infrastructure. Knowing what sorts of disasters to plan for is the first step in disaster recovery planning. The following sections describe a few basic disaster types.

Physical Site Disaster

A site disaster is anything that keeps users or customers from reaching their desired office location. Examples include natural disasters such as floods, fires, earthquakes, hurricanes, or tornadoes that can destroy an office. A site disaster also can be a physical limitation, such as a damaged bridge, bomb scare, or building evacuation that would keep the employees from working at their desks. When only physical access is limited or restricted, a remote access solution could re-establish connectivity between users and the corporate network. Refer to Chapter 26, "Remote and Mobile Access," for more information in this area.

Power Outage

Power outages can occur at any time unexpectedly. Some power outages are caused by bad weather and other natural disasters, but other times they can be caused by high power consumption. In the summer of 2001, many businesses located in northern California in the United States were left without power because the power company could not reroute power from the rural areas to the highly utilized areas such as Silicon Valley. Many businesses were unable to function because the core of their work was conducted on computers.

Network Outage

Organizations that use computer networks internally or externally to the Internet are all susceptible to network outages, causing loss of productivity and possibly revenue. Problems include a network line being mistakenly cut, the Internet service provider being purchased or sold, and a new organization inadvertently disconnecting the main connection for the office. Or, a network router or other network equipment, including hubs, switches, network interface cards, or even network cables, can fail.

Server Hardware Failures

Server failures are the type of problem most organizations plan for because they seem to be the most common disaster encountered. Server hardware failures include failed motherboards, processors, memory, network interface cards, disk controllers, power supplies, and, of course, hard disks. Each of these failures can be dealt with differently, but to achieve system-level fault tolerance, a cluster should be implemented using either Windows Server 2003 Cluster Services or network load balancing.

Hard Drive Failure

Hard drives have been singled out as a possible cause of server hardware failure. Windows Server 2003 supports hot-swappable hard drives, but only if the server chassis and disk controllers support such a change. Windows Server 2003 supports two types of disks: basic disks, which provide backward compatibility, and dynamic disks, which allow software-level disk arrays to be configured without a separate hardware-based disk array controller. Also, both basic and dynamic disks, when used as data disks, can be moved to other servers easily to provide data or disk capacity elsewhere if a system hardware failure occurs and the data on these disks needs to be made available as soon as possible.

Note

If hardware-level RAID is configured, the controller card configuration should be backed up using a special vendor utility, or it may need to be re-created from scratch if the disks are moved to a new machine.

Software Corruption

Software corruption can occur at many different levels. There could be software corruption in a file's access control list (ACL), an operating system's file, or an application could have mistakenly overwritten files or folders. Systems providing access to databases are also susceptible to database corruption, so special care should be taken to be sure the databases are frequently backed up and that proper backup and restore techniques are understood.