[ar0]

While this is true for a high availability data center whose customers expect their website to be up 100% of the time, this article talks about storage infrastructure for their archiving service (C14). Restoring data from C14 will take multiple hours anyways, so networking downtime (or even power downtime, assuming they have enough backup power to safely power down their disks) will be of much lesser concern in the given use case than physical protection from natural or man-made disasters, which would destroy the archived data, or theft.

The main argument I would agree with is that it would maybe be cheaper (and definitely more secure) to keep data redundantly in two data centers sufficiently spread out to not be affected by a singular disaster than in a single hyper-secure data center.

[walrus01]

If you're building a relatively slow/cold storage archive datacenter I can think of a lot cheaper, less labor intensive ways to do it than retrofitting an underground bunker... I am assuming they either acquired the bunker for "free" or it has some purpose other than technical (marketing/sales/look how secure your data is!!!).

[nickparker]

Not to mention, a bunker in Paris. If it's not speed-critical, it should be off in some mountain or field not an urban center.

[walrus01]

And isn't electricity in Paris something like 18 euro cents per kWh? Now your datacenter is eating expensive electricity and requires special expensive cooling systems all year round, because even in the middle of winter there's no easy way to do free-air cooling of an underground bunker.