[walrus01]

I work in telecom and this is fun to look at, but I bet I could take their facility off the net with 4 guys and two rented backhoes.

Awesome physical security is cool for customer tours (SwitchNAP Las Vegas, anyone?) but the real measure of redundancy is to what extreme you have 1+1 or N+1 everything for your support gear (cooling, generators, UPS, giant -48VDC battery plant, rectifiers, etc), and the layer 1 diversity of your fiber routes in and out of the facilities. And the diversity of the upstream carriers from your east/west/north/south fiber routes, the topology of how your dark fiber link out of the facility reaches the nearest major IX points.

Diversity of power feeds: Do they have redundant parallel A and B side high voltage electrical feeds coming from the local grid utility, fed from two separate geographically distinct substations? Really important datacenters in the US and Canada do.

On a facility side, something like this which is arched vaults underground will be a cooling system nightmare, driving up costs considerably vs. an aboveground structure where you can easily locate heat exhangers/cooling towers and free air cooling systems on concrete pads next to a box shaped building. There's ways to achieve up to 10kW/cabinet cooling density in that old buried bunker but it will be a lot costlier to do than in, for example, a retrofitted warehouse-like structure that was formerly a newspaper printing plant.

[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.