What is offsite backup?
Offsite backup is a copy of backup data kept at a different physical location from the systems it protects. Its purpose is to survive events that affect a whole site, such as fire, flood, power loss or theft, which would destroy both production and any backups stored next to it.
How is an offsite copy created?
There are three established methods, and many organizations use more than one.
| Method | How the copy travels | Typical freshness |
|---|---|---|
| Tape rotation | Cartridges moved to a vault by courier | Days, set by the collection schedule |
| Copy to a second site | Backup copy job over a network link | Hours or less |
| Copy to cloud object storage | Backup software writes to a cloud bucket | Hours or less |
How far away should an offsite copy be?
Far enough that one event cannot reach both locations. A second room in the same building protects against equipment failure and a contained fire. Another building on the same campus adds protection against the loss of one building. A site in another city covers regional events such as flooding or an extended power failure. Regulations in some sectors set a minimum distance. Greater distance generally means a slower or more expensive link, so the choice balances risk against the cost of keeping the copy current.
Is an offsite copy protected from ransomware?
Distance protects against physical events. It does nothing against an attacker who reaches the offsite repository over the network with stolen credentials. For that, the copy also needs to be offline, as with ejected tape, or immutable, so that it cannot be changed or deleted before its retention ends. The 3-2-1-1-0 rule lists these as separate requirements for that reason. Logical air gap describes how an online copy can be isolated.
What should be checked about an offsite copy?
Four things. How old the newest restore point is at the offsite location, measured daily. Whether everything needed to use the copy, including encryption keys and a way to rebuild the backup server, is available away from the primary site. How long a restore from that location takes. And whether a restore has actually been run from it. What the second copy needs after a site failure goes through each.
Frequently asked questions
Is cloud backup the same as offsite backup?
Cloud storage is one way to hold an offsite copy. Offsite backup is the broader idea of keeping a copy somewhere else.
Does replication count as offsite backup?
Replication to another site gives an offsite copy of current data, but it also copies deletions and corruption. Backups keep earlier points in time.
How often should the offsite copy be updated?
Often enough that the data lost with the primary site is acceptable. For most organizations that means at least daily.