Interesting that you are asking for the dirt given that DiRT stands for Disaster and Recovery Testing, at least at Google.
Every year there is a DiRT week where hundreds of tests are run. That obviously requires a ton of planning that starts well in advance. The objective is, of course, that despite all the testing nobody outside Google notices anything special. Given the volume and intrusiveness of these tests, the DiRT team is doing quite an impressive job.
While the DiRT week is the most intense testing period, disaster preparedness is not limited to just one event per year. There are also plenty tests conducted througout the year, some planned centrally, some done by individual teams. That's in addition to the regular training and exercises that SRE teams are doing periodically.
I found a comment that was factually incorrect and I felt competent to comment on that. Regrettably, I wrote just one sentence and clicked reply without providing any credentials to back up my claim. Not that I try to hide my identity, as danhak pointed out in https://news.ycombinator.com/item?id=28751644, my full name and URL of my personal website are only a click away.
I unfortunately cannot edit the parent comment anymore but several people pointed out that I didn't back up my claim or provided any credentials so here they are:
Google has multiple independent procedures for coordination during disasters. A global DNS outage (mentioned in https://news.ycombinator.com/item?id=28751140) was considered and has been taken into account.
I do not attempt to hide my identity here, quite the opposite: my HN profile contains my real name. Until recently a part of my job was to ensure that Google is prepared for various disasterous scenarios and that Googlers can coordinate the response independently from Google's infrastructure. I authored one of the fallback communication procedures that would likely be exercised today if Google's network experienced a global outage. Of course Google has a whole team of fantastic human beings who are deeply involved in disaster preparedness (miss you!). I am pretty sure they are going to analyze what happened to Facebook today in light of Google's emergency plans.
While this topic is really fascinating, I am unfortunately not at liberty to disclose the details as they belong to my previous employer. But when I stumble upon factually incorrect comments on HN that I am in a position to correct, why not do that?
The safe in question contained a smartcard required to boot an HSM. The safe combination was stored in a secret manager that depended on that HSM.
The engineer attempted to restart the service, but did not know that a restart required a hardware security module (HSM) smart card. These smart cards were stored in multiple safes in different Google offices across the globe, but not in New York City, where the on-call engineer was located. When the service failed to restart, the engineer contacted a colleague in Australia to retrieve a smart card. To their great dismay, the engineer in Australia could not open the safe because the combination was stored in the now-offline password manager.
Every year there is a DiRT week where hundreds of tests are run. That obviously requires a ton of planning that starts well in advance. The objective is, of course, that despite all the testing nobody outside Google notices anything special. Given the volume and intrusiveness of these tests, the DiRT team is doing quite an impressive job.
While the DiRT week is the most intense testing period, disaster preparedness is not limited to just one event per year. There are also plenty tests conducted througout the year, some planned centrally, some done by individual teams. That's in addition to the regular training and exercises that SRE teams are doing periodically.
If you are interested in reading more about Google's approach to distaster planning and preparedness, you may be interested in reading the DiRT, or how to get dirty section from Shrinking the time to mitigate production incidents—CRE life lessons (https://cloud.google.com/blog/products/management-tools/shri...) and Weathering the Unexpected (https://queue.acm.org/detail.cfm?id=2371516).