The 3-2-1 backup rule, explained through real cases

Almost every company has “backups”. Very few have one they have ever restored from. The difference between the two is always discovered on the worst possible day.

What the rule says

It is an old rule, simple and still valid:

• 3 copies of the data — the original and two copies.
• 2 different types of media — for example the server disk and an external drive, or disk and cloud.
• 1 copy in another physical location.

Why each number

Why two copies, not one

Because a copy can fail at exactly the moment you need it. An external drive kept in a drawer and used once a month has a real chance of not spinning up when it matters.

Why two types of media

The same disks, bought on the same day from the same batch, tend to fail around the same time. If the backup sits on a disk identical to the original, you have two devices of the same age and the same wear.

Why another location — the most ignored part

A fire, a flood, a break-in or a lightning strike does not distinguish between the server and the backup drive next to it. This rule looks excessive until the day it is not.

What ransomware changed

Programs that encrypt your files and demand money go looking across the network for backups too. If the backup drive is permanently connected and reachable, it gets encrypted along with everything else.

So a fourth requirement now sits alongside the three numbers: at least one copy that cannot be deleted or modified — a drive physically disconnected after copying, or a service that keeps versions which cannot be deleted for a set period.

The five-minute test

Do not ask “do we have backups?”. Ask this:

1. Pick any file, deleted or changed last week.
2. Ask for it to be recovered, now, in front of you.
3. Time it.

If it cannot be done, you do not have backups — you have a process that runs. If it takes a day, find out whether the company can survive a day.

What almost always gets forgotten

• Email mailboxes. Many companies back up the server but not the email, which is where the commercial history actually lives.
• Configuration. You have the data, but not the settings that make the application work with it.
• Files on people's laptops. That is often where quotes and contracts in progress sit.
• The website and its database, if they are with a provider who “takes care of it”. Worth checking exactly what that means.

The two questions before any solution

How long can the company operate without this data? An hour, a day, a week? The answer decides how fast restoration has to be.

How old can the recovered data be? If the backup runs overnight and the problem happens at four in the afternoon, you lose a full day of work. Sometimes that is acceptable. Sometimes it is not.

Everything else — which technology, which provider — follows from those two answers. If you have never put them into words, that is the most useful thing you can do this week.

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