By second disk failure do they mean that the disks on both the primary and fallback servers failed? Or do they mean that two disks (of a RAID1 or similar setup) in the fallback server failed?
The latter is understandable, the former would be quite a surprise for such a popular site. That means that the machines have no disk redundancy and the server is going down immediately on disk failure. The fallback server would be the only backup.
The latter is understandable, the former would be quite a surprise for such a popular site. That means that the machines have no disk redundancy and the server is going down immediately on disk failure. The fallback server would be the only backup.