Suppose you wanted to make sure you never lost any data. Yes, you can replicate it numerous times, you can push to the far corners of the globe (does a globe have corners?), you can make sure it sits on multiple formats.
But all these things have one drawback: they're vulnerable to environmental disasters. One company, Axxana, reckons it has an answer: an aircraft-style black box.
Data protection's a big deal these days, what with compliance issues, and a growth in the volumes and importance of electronic information. But while it's unlikely that there'll be a fire in your data vault at the same time as your pair of mirrored datacentres get flooded, the more copies of your data you maintain, the more expensive and difficult to manage they become. So one primary copy is usually enough, plus an archive. That balance of risk against cost is the one that's often struck.
There are other issues involved too, not least of which is the ultimate limiting factor (at this stage of human knowledge anyway): the speed of light. If you're running a busy datacentre and you want to mirror it to ensure that, if bad things happen, you always have a copy of your data, then you can't base the second facility too far away.
Usually, the mirrors are within 25 miles or so, according to Axxana CEO Eli Efrat, to avoid latency problems. This means that both facilities could be vulnerable to the same environmental or terrorist event. Even so, it might not be a problem -- apart from the data that's in transit from database to disk. Uncommitted data could be on its way to complete a transaction to the second datacentre. If disaster strikes, that data could disappear before it's written to the storage medium. It's worse of course you don't happen to have access to a mirrored datacentre.
Axxana's answer is a black box in the primary datacentre, attached to the storage system, that records everything. Even if the datacentre is reduced to rubble, Axxana reckons its Phoenix Black Box, based on solid state storage, will survive and allow you to recover that data.
You can't crush it, you can't set fire to it and it's watertight -- so says Axxana, anyway, claiming that it'll withstand the force of a building collapsing onto it, 2000 degrees C, high levels of shock and long periods of immersion. After you recover it, you hook it up and it restores the data.
It sells for somewhere in the region of $200,000, so you really will have to conduct a proper cost-benefit analysis. I suppose someone must need that level of survivability...