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3-2-1 backup: The Golden Rule for disaster recovery

August 27, 2018

Article courtesy of Yeo & Yeo

When it comes to maintaining a disaster recovery plan for your organization, the 3-2-1 Backup Rule is the gold standard. For many years, we have worked with clients to implement effective disaster recovery plans, and we live by this rule to keep their data protected. 

What is the 3-2-1 Backup Rule? Simply put, organizations should make three copies of their data available on two different media, with one stored offsite. While it sounds easy enough, many organizations don’t follow it. Like anything else, you still need to focus on the details to ensure your data can be recovered. 

Why isn’t one backup enough? 
Imagine that you keep your original data on one device, and its backups are on a second device with the same characteristics, and their failures are statistically independent. For example, if device #1 has a probability of failure that is 1/100 (and the same is true for device #2), then the probability of failure of both devices at the same time is: 1/100 * 1/100 = 1/10,000

This means that if you have your primary data (on device #1) and two backups of it (on devices #2 and #3), and if all devices have the same characteristics and no common failure causes, then the probability of failure of all three devices at the same time is: 1/100 * 1/100 * 1/100 = 1/1,000,000

For this reason, having more copies of your data means you will have less risk of losing data during a disaster. In short, if your data is important to you, be sure to make at least two backup copies.

Use two different media types 
Copies of your data should always be on multiple device types. Media storage options include tapes, external hard drives, USB drives, SD cards, CDs, DVDs, or even floppy disks, or on two internal hard disk drives in different storage locations.

Keep one data source offsite 
If your office were to be hit with a disaster, like a fire or a tornado, having multiple backups in one location would not do you any good. By keeping the data replicated offsite, you significantly increase your recovery percentage. 

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