What is the 3-2-1-Rule for Backing up Data?

3-2-1 Data Backup Peter Krogh

Even the best computer systems crash; even the brightest people can make a mistake. And it’s not so much a matter of if a disaster will strike, but when. So, it’s imperative that organizations protect their critical data by backing it up. While most businesses have some form of on-site data backup, this is no longer enough. To have a solid data backup plan, organizations should follow the 3-2-1 rule of data backup.

The 3-2-1 Backup Rule coined by Peter Krogh

Storing copies of data both locally and in the cloud presents several distinct advantages. This method of backup has become so popular that there’s even a name for it: the 3-2-1 backup rule.

This rule is attributed to Peter Krogh, a commercial photographer who is also widely considered an expert in Digital Asset Management (DAM). While Krogh certainly isn’t the first person to realize the benefits of onsite and cloud storage, he is responsible for the catchy name as described in his book, The DAM Book: Digital Asset Management for Photographers. The rule states:

  • 3 copies of your data should be maintained
  • 2 independent storage mediums should be used
  • 1 backup copy should be stored offsite

Now, let’s look at each aspect of the 3-2-1 backup strategy in more depth.


3 backup copies of your data should be maintained

The reason for keeping three copies of your data (primary plus two backups) is to minimize risk by playing the probability game. In the following scenarios, imagine that all devices have the same characteristics, yet no common failure causes. Now, let’s pretend the probability of failure for each is 1/100.

If you maintain primary data on one device, you have 1/100 chance of losing your data. Maintain a secondary device, and your chances of losing data drop to 1/10,000 (1/100 x 1/100). Now, maintain three backups and the risk drops to  1/1,000,000 (1/100 x 1/100 x 1/100). Those odds sound a lot better, right?

Not only have you greatly reduced risk, you’re offsetting situations in which the primary and secondary copies are stored in the same physical location.


2 independent storage mediums should be used

In the above scenario, we imagined that there were no common failure causes across all devices. Of course, this is the real world, and oftentimes when one disk fails another will fail shortly thereafter.

The 3-2-1 rule recommends using two types of storage to avoid such a scenario; for example, an internal hard drive PLUS a removable medium (tapes, external hard drives, USBs, etc) or two internal hard drives stored in different locations.


1 backup copy should be stored offsite

Keeping all your data in one location is akin to putting all your eggs in one basket. It’s not a wise strategy! Physical separation between copies is a necessity, especially for small and medium-sized businesses (SMBs) that have no remote or branch offices in which to store backups. For these SMBs, storing online backups in the cloud is an ideal solution.

Not only do online data backup solutions add another layer of data protection, a reliable  data center is better equipped to handle threats such as fires, floods, or theft because they’re designed for them. Reputable data centers will have fire suppression systems, hurricane-rated structuring, environmental controls, raised flooring, biometric scanning, backup power supplies, and 24/7 surveillance.


DSM works with Veeam, Zerto, and Commvault

If you’re already using on-premise data management (DM) software such as Veeam, Zerto, or Commvault, you can now get physical and virtual backups offsite through DSM to replicate virtual machines—without the cost or complexity of building and maintaining off-site infrastructure. DSM cloud data backup services work seamlessly with DM software for fast and secure backups controlled within their interface. With DSM and data management software, you’ll benefit from the following:

  • Hosted Offsite Backups. Easily send backups through a secure SSL connection to DSM’s enterprise-grade data center to provide off-site protection.
  • Complete Visibility and Control. Manage your backups and perform restores directly from the DM software console.
  • End-to-End Encryption. Protect data in-flight and at-rest for compliance and added security.
  • Virtual Machines and Physical Servers. Protect both virtual machines and physical servers, consolidating the data protection plan for your entire environment.

They say it’s better to be safe than sorry, and the 3-2-1 Data Backup Rule is one way you can ensure the safety of your most critical data. Want to learn more about DSM and our compatibility with DM software? Contact our IT experts today.

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