Hardware Problems.
In the early days of computer networks and servers, this is before the days of viruses. We only did the backup just in case the hardware failed. And in those days the hardware we were worried about was the hard drive. For years this was the only moving part in the computer, and it was the component that held all of the data. After years of operating, no matter how good the hardware is. Moving parts fail. And if this was your only copy of your data. It would be lost. 

Disaster Recovery.
Of course, there is always the possibility of a natural disaster. Earthquakes landslides, and floods. It was back then that we coined the phrase Disaster Recovery.
Of course, anyone of these things would be a disaster for your company and your data.

Along the line of disaster recovery, not only do we need to make sure we have backed up the data that your company depends upon. We must also backup the network operating system. This is far more important in a small company that only has one server.

If you have more than one server on your network, that is providing domain controller functions (DC), then your domain information, for example, user names, passwords. It is stored on all of the domain controllers in your network. However, if you only have one server in your network. This information required to run your network domain is only on the domain controller server. You can, of course, reinstall the network on a new server. However, you will need to reinstall every single workstation into this new network. Even if they were previously installed in the network even if the network was using the same domain name.

However, Disaster Recovery and Preparedness has a whole new meaning in the days of Ransom where. 

If we were only looking at the scenario of a hardware failure. Copying the data and even the domain controller information to an another hard drive connected to the same computer would be good enough. Playing the odds that two hard drives would fail at the same time is extremely rare. However, this does not protect you from a natural disaster, a fire, and the big one these days and encryption virus or ransom where.

Bare metal restore
In the case of a hardware problem. If it is the bootup drive (Drive C:) that fails. You need to install a new drive and then do a restore onto a bare metal server, something that has no operating system installed nothing on it just the bare metal. This would also be the case for a server that was totally destroyed by a flood, earthquake, or some other natural disaster.

Malicious software (a.k.a. malware), or Ransomware.
Malware and Ransomware modifies the current files found on the server or workstation to either make it unusable or hold it for ransom. For this reason, it is very important to store your backup files somewhere else other than connected to the server/computer you are trying to protect. Also you must use backup versioning. This is required so you can go back in time to a point when you know for a fact that the files you need were not modified by a virus.

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