[Godel_unicode]

Assuming you have data that is tiny enough to fit anywhere other than the cluster you were using. Assuming you can afford to have a second instance with enough compute just sitting around. Assuming it's not the HDDs, RAID controller, SAN, etc which is causing the outage. Assuming it's not a fire/flood/earthquake in your datacenter causing the outage.

...etc.

[killjoywashere]

Ah, yes, I will never forget running a site in New Orleans, and the disaster preparedness plan included "When a named storm enters or appears in the Gulf of Mexico, transfer all services to offsite hosting outside the Gulf Coast". We weren't allowed to use Heroku in steady state, but we could in an emergency. But then we figured out they were in St. Louis, so we had to have a separate plan for flooding in the Mississippi River Valley.