How to follow the 3-2-1 rule – Data Backup

Every business admin responsible for a company’s digital data should have a backup. Backup is king and when the day comes that ….. hits the fan, you will be the HERO!

One of the timeless rules that can address any failure scenario is called the 3-2-1 backup rule.

The 3-2-1 rule became a popular concept thanks to Peter Krogh, a well-known photographer who wrote that there are two groups of people “ those who have already had a storage failure and those who will have one in the future”. In other words, the 3-2-1 backup rule means you should:

  • Have at least three copies of your data.
  • Store the copies on two different media.
  • Keep one backup copy offsite.


1. Have at least three copies of data

By three copies, I mean that in addition to your primary data, you should also have at least two more backups.

Why isn’t one backup enough?  Imagine that you keep your original data on device #1 and its backup is on device #2. Both devices have the same characteristics, and their failures are statistically independent (they have no common failure causes). For example, if device #1 has a probability of failure that’s 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 x 1/100 = 1/10,000

Introduce device #3 to keep another copy 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 will be:

1/100 x 1/100 x 1/100 = 1/1,000,000

If you’re thinking to yourself that “1/10,000” seem like great odds to stop right there with device #2, then think again. If device #1 and #2 share the same environmental and hardware characteristics, then the odds drop. What do I mean by environmental? Well if the devices are in the same building, using the same power, and under the same security, then they share the same environment. Ask yourself, can you control natural disasters, power surges, fire or theft? What do I mean by Hardware? When it comes to hardware, the cheaper the purchase price, the cheaper the materials that were used to create its components. This will influence hardware reliability.


Do you know how much your data is worth? Then try working it out like this

Example: “Hours to recreate” x “Loss of income” x “Loss of credibility in the eyes of your clients”


2. Store the copies on two different media

In the previous section, we assumed that there were no common failures across all 3 devices where data copies are stored. If your primary data and backup data are in the same place such as a server with disks in RAID ( Redundant Array of Independent Disks), it is not uncommon after one disk fails, to experience failure of another disk from the same storage around the same time.

That’s why the 3-2-1 rule suggests that you keep copies of your data on at least two different storage types, such as internal hard disk drives and removable storage media (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


3. Keep one backup copy offsite

Identifying the environmental characteristics of where your data backups reside is important. Having an offsite backup copy plan for situations which are out of your control such as natural disaster, fire or theft. will lead towards you being the Hero if one of these events unfortunately happen.

Storing copies of data to the cloud is one the best options available to you. Instead of using portable hard drives or tapes which you take home with you or the hassle of having to remind someone in the office. A Cloud backup service is an easy process to setup, it lets you set automation in the storage of data and allows you to restore whenever you need to.


Getting the right Cloud backup service for your business digital data is important. Understanding which parts of your data and the systems that run them are key to setting out a plan which will allow your business to recover from an unfortunate event.