Ignore The Rule Of 321 At Your Peril

Ignore The Rule Of 321 At Your Peril

Recently on the DocumentSnap newsletter I wrote about an important concept in protecting your paperless documents: The Rule of 321.

The general concept is that you want your data in as many places as possible:

  1. Have at least 3 copies of your data – In other words, have your original PDFs (1 copy) and 2 backups (2 more copies to make 3).
  2. Keep these backups on 2 different media – Don’t have your originals and your backups on the same drive. Don’t just rely on CD or tape backups. What happens if you no longer have a CD or tape drive? If you’re old like me, you’ll remember ZIP drives.
  3. Store 1 backup offsite – Whatever happens to your computer could happen to your backup drive too. Keep at least one copy in a different location.

I had a lot of responses to that newsletter, but here is a situation I’ve certainly never heard of from a DocumentSnap reader. Here’s what they had to say:

Your article gave me a chuckle. Here's why.

I'm very careful about backing up. I assume that one day the burglars will come and take my IT equipment or the house will burn down or encryption malware will – despite my extensive anti-malware precautions – render my data inaccessible. Several years ago a nearby lightning strike generated a voltage spike/current surge that destroyed my PC (the IT repair shop found one of the cards covered with Lichtenberg discharge figures and the HDD controller no longer worked).


  • My priceless family photos and videos and music are kept on a network server with RAID redundancy.
  • Those files and all the other data on my PC and other office equipment are backed up weekly to an external hard drive (HDD) which is kept in the vault of a local bank conveniently situated 5 minutes by bike from my home.
  • A second HDD which is kept at home is used for in-between backups during the week, e.g. following creation of a large number of files.
  • I unplug everything if there is a thunderstorm in the vicinity or forecast, e.g. during the night.
  • A log of the backups is kept on a cloud server so that, when disaster strikes and I have to buy new equipment and restore images, I'll know what is where.
  • I regularly check my external HDDs with the free Seagate disk checker. A Seatools check threw up an unacceptable failure rate of one of my external HDDS a few months ago and the HDD was scrapped.

100% sure. Belt-and-braces. Right ? Wrong. Our village is halfway up a gently sloping hillside in a river valley. The bank with its vault is around 250 metres below us. A few years ago there was a catastrophic storm. The downhill rush of water washed away the roads connecting the village to the outside world and part of that water flowed into the bank vault. When I went to collect my HDD for the weekly backup they were still pumping out the vault. The high water line around the vault stopped just below my strongbox so I was able to take out a still-dry and working HDD but a couple of inches more and it would have been soaked.

So all was fine because I still had my intact data back home and the backup HDD had just avoided a soaking but this was a lesson. Even if the backup data is offsite – in a bank vault, for Heavens' sakes – that off site may be insecure.

This is such a great example of the need to keep multiple backups in different locations. Now, it is very possible that where you live may never have bank vaults filling up with water, but it is very possible that something is going to happen to one or more of your devices.

Ignore the rule of 321 at your peril!

Do you have any similar stories of backup intentions gone awry? Leave a comment and let us know.

About the Author

Brooks Duncan helps individuals and small businesses go paperless. He's been an accountant, a software developer, a manager in a very large corporation, and has run DocumentSnap since 2008. You can find Brooks on Twitter at @documentsnap or @brooksduncan. Thanks for stopping by.

Leave a Reply 1 comment

Steven Buehler - March 15, 2017 Reply

On my Windows machine, my default document, video, and picture directories sync with OneDrive with nearly all my scans in OneNote both in PDF and viewable image form. Also, most if not all network-attached storage has some way to back itself up online (Seagate Personal Cloud, which I have, is able to back itself up to Amazon S3, Baidu (pcs), Box, Dropbox, Google Drive, Strato HiDrive, Yandex.Disk, OneDrive, or any combination thereof, as often as hourly).

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