Most computer users are at least somewhat aware of the importance of keeping backups of data. I suspect that most computer users are also less careful than they ought to be when it comes to protecting those backups.

TL;DR: If your digital data is worth anything significant to you, then you need to keep multiple, redundant encrypted backups of it in physically separate locations

Why extra backups matter

If you run a business, you are probably well aware of the enormous economic risk posed by data loss. Even if you don't have any "mission-critical" data with a clear financial value, how would you react if all your family photos were irretrievably lost?

Computers are not reliable. Hard drives crash, power supplies burn out, operating systems occasionally turn rabid, data can be corrupted. An up-to-date local backup (on a separate hard disk, of course) is your first line of protection against the dreaded "it just died and took my files with it".

A local backup is not enough, though. Houses can burn down. Burglars can steal equipment. Sewers can flood, earthquakes can collapse the building, or an ill-placed lightning strike might burn out every electronic device in the vicinity. Your meticulous daily backup routine means nothing if the backup disk is stored in a desk drawer under the computer itself.

To protect against all of these possibilities, you need to keep redundant copies of your backup data in physically separate locations with different risk profiles. If you commute more than a few kilometres to work, there's a good chance your office is sufficiently different from your house that any disaster short of a thermonuclear weapon is unlikely to completely wipe out both locations- and if World War III does start in your hometown, you probably won't be around to care.

My solution:

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Daily backups are run automatically using Cobian, and are stored on a local disk (an extra internal drive in my case; for laptops, use an external hard drive).

A couple of times a week, I bring home one of two external hard drives that are stored at a remote location. A backup is run, and the drive is returned to storage the next day. The two drives are never brought home at the same time.

These backups are incremental- each one adds only the files changed since the last one- which saves time and disk space, and also allows me to recover only a handful of corrupted files if necessary.

In this manner, we can ensure that two physically separate locations each always have a full copy of the data. If one building is burned/flooded/nuked/robbed, the data is still protected at the other location.

Securing off-Site data

There is an obvious, gaping hole in the plan as stated: A complete collection of your personal and/or business files is sitting on a disk in someone else's building.

That's far too big a security hole to ignore. The solution, thankfully, is very well understood: Encrypt the backup disks. Many backup tools offer built-in encryption, but I don't like using them; it may be hard to recover the data later, and there's often no way to know how thoroughly the encryption has been validated and tested.

A better option is to secure your data using a tool designed by and for the world's top computer security researchers: TrueCrypt. Format your external disks in TrueCrypt, using whole-disk encryption, and choose a good passphrase- a few random words, maybe in a couple of different languages, will be far more secure than a hard-to-remember string of random letters and numbers.

90% of thieves, upon stealing such a disk, will find nothing at all on it. The 10% of thieves who are smart enough to say "aha, it's encrypted" will recognize the encryption format but be unable to break it. The CIA, if they get their hands on it, *might* eventually be able to pry in if they devote a ridiculous amount of resources to breaking the code. But you- using your passphrase and any computer with TrueCrypt- can instantly recover the entire data set.

What about the cloud?

In a word, no.

Unless you have a 50 Mbps unlimited Internet connection (ha!) and a trustworthy cloud service provider (double ha!), cloud backups are obscenely slow to run and can't guarantee any appreciable level of security unless you've encrypted the data yourself. One backup run, for me, would burn through an entire month's internet bandwidth cap and would take many days to run.

Scalability: Handling huge amounts of data

Hauling hard disks around scales quite well as long as the total of all your data is no more than half the capacity of the portable disks. (It is of course preferable to write a new backup before you delete the old one, hence why you shouldn't max out your backup disks.) With today's 2 and 3 terabyte drives, the working limit is 1 to 1.5 TB, which is more than most people will create in a lifetime.

If you shoot a lot of video, though, you'll quickly run into "drive full" errors. Shuttling partial backups back and forth on hard drives is one option; permanently archiving multiple copies of data on optical discs is another. If you have more than a terabyte or two of active, working data, it's probably time to look beyond consumer gear and shell out some cash for business-class storage and backup systems. But that's another story.