Timely Backup: Understanding The 3-2-1 Backup Rule

Monday, 13 November 2017 by Philipp Lohberg

Data loss is a topic that is getting more and more explosive. Attacks from outside and inside the company, water or fire, bad sectors on the storage medium - there are numerous ways to lose important data. And: The human being is responsible for 25 % of all data losses - the cleaning lady, who uses the power socket to which the backup drive is also connected for her vacuum cleaner, is still the smallest danger.

The only reasonable solution to deal with problem data loss is a timely backup. The preparation of a good backup strategy is certainly reasonable, but to wait (and for a certain amount of time having no backup) is grossly negligent.

The 3-2-1 backup rule is a viable method to have the greatest possible security.

Your data should be stored 3 times: Once they are present on your working system, two backups provide security.

You should use 2 different technologies. There are plenty of available: NAS, external hard drives, flash memory, magnetic tapes, DVDs, the cloud, etc.

1 of the backups should always be kept out of the house or company premises.


Why this effort?

3 x - Three-time data storage statistically minimizes data loss. Suppose you save the original data to disk 1 and the backup to disk 2. If the failure probability of disk 1 and disk 2 is 1/100 the probability of simultaneous failure of both drives is 1/100 * 1/100 = 1 / 10,000. With three backups, the probability decreases to one in a million.

2 (Two) different technologies – ie media - reduce the probability even further. It is not uncommon for two devices from the same batch to have a similar life – everyone knows this phenomenon in case of simultaneous failure of light bulbs in the home. With RAID systems, it is also not uncommon for a hard disk to die too shortly after the failure of another disk.

Keeping 1 backup in a different location is recommended in any case. In case of problems with flood or fire, theft or other disasters, not all backups will be lost. Keeping a backup version in a bank safe, branch office, private apartment or at friends home is not very complex or even problematic, but it can save your company from ruin in case of damage.

If you back up your data after the 3-2-1 backup rule, you are on the safe side. But in general, the safest backup is the one that you create right now - without thinking of rules and regulations. Waiting for an ingenious backup strategy can be dangerous (what if something happens during the waiting period?). Remember a fresh backup - even if it isonly on a self-made CD - is a fresh backup.