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Corporate networks don’t often use duplicate servers, and that’s because there are some major disadvantages associated with using them:

■ You must keep current backups. Because the duplicate server relies on a current backup, you must back up every day and verify every backup, which is time-consuming. To stay as current as possible, some companies run continuous backups.

■ You can lose data. If a server fails in mid-afternoon and the backup was run the evening before, you will lose any data that was placed on the server since the last backup. This may not be a big problem on servers that aren’t updated frequently.

Cold Site

A cold site cannot guarantee server uptime. Generally speaking, cold sites have little or no fault tolerance and rely completely on efficient disaster recovery methods to ensure data integrity. If a server fails, the IT personnel will do their best to recover and fix the problem. If a major component needs to be replaced, the server stays down until the component is replaced. Errors and failures are handled as they occur. Apart from regular system backups, no fault tolerance or disaster recovery methods are implemented.

This type of site has one major advantage: It is the cheapest way to deal with errors and system failures. No extra hardware is required (except the hardware required for backing up).

Power Management

key element of any fault tolerance plan is a power management strategy. Electricity powers the network, switches, hubs, PCs, and computer servers. Variations in power can cause problems ranging from a reboot after a short loss of service to damaged equipment and data. Fortunately, a number of products are available to help protect sensitive systems from the dangers of lightning strikes, dirty (uneven) power, and accidental power cable disconnection, including surge protectors, Standby Power Supplies, uninterruptible power supplies, and line conditioners. What you use depends on how critical your system is (whether you decide that it is a hot, warm, or cold site). At a minimum, you should connect individual workstations to surge protectors, and network hardware and servers should use uninterruptible power supplies or line conditioners. Critical operations, such as ambulance corps and hospitals, typically go one step further and also have a gas-powered backup generator to provide long-term supplemental power to all systems.

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