The 3-2-1 backup rule, explained without the jargon
Three copies of your data, on two different types of storage, with one copy kept somewhere else entirely. It's simple on purpose.
The 3-2-1 rule is one of the oldest pieces of advice in backup and disaster recovery, and it's stuck around because it's genuinely simple and genuinely effective: keep three copies of your important data, store them on two different types of storage, and keep at least one copy somewhere physically or logically separate from the rest.
The reasoning behind each part is practical rather than arbitrary. Three copies means a single failure — a corrupted file, a broken drive — doesn't cost you the only backup you had. Two different storage types (say, a local backup plus a cloud backup) means a single type of failure, like a specific piece of hardware dying, doesn't take out every copy at once. And one copy kept elsewhere protects against the scenario where something affects your whole location — a fire, a flood, a theft, or in modern terms, ransomware that spreads across everything connected to the same network.
In practice, for most small businesses today, this often looks like: your live working data, an automated cloud backup running in the background, and a separate backup service or provider that isn't the same as your everyday cloud storage — so a single compromised account can't wipe out everything at once.
The rule is decades old and the technology behind it has changed completely, but the underlying logic — don't let one failure take out everything — hasn't dated at all.