[crote]

There's also just an upper limit to the kind of risk you can reasonably defend against.

An out-of-control wildfire levels the entire city? The Big One hits the Bay Area? The entire city is flooded for a few months because the levees break during a Cat5 hurricane? Yeah, your DC will be completely ruined. And even if it isn't, you're probably not getting any outside power, generator fuel, or repair technicians for a while.

No matter how much money you pump into hardening your own super-bunker DC, there will always be disasters you aren't prepared for. At a certain point it just makes more financial sense to abandon the idea of invulnerability and build a redundant site a few states over. Accept that you will occasionally lose one, and only protect against incidents where mitigation is cheaper than occasionally rebuilding.

[earthboundkid]

In terms of deliberate attacks on a DC, an adversary that can bomb a blast resistant bunker can easily bomb the data lines going in and out, to say nothing of external power supplies. I guess you can at least repair the lines after the attack, but it's pretty easy to knock it offline if that's your goal. I just don't see the value in making a DC blast resistant compared to the huge costs.