Yesterday, the network of Linode over at HE.net has suffered a major outage -- supposedly, he.net has had "one out of eight" of their power generators fail, which, apparently, has one way or another resulted in the whole Linode Fremont cloud going down for five whole hours (2015-05-29T18:30/23:30 PT). There have been some reports that supposedly the network core was the part without power, however, upon coming back up, it appears that all servers might have been power cycled, too.
What's the best practice for supplying the power to the servers?
Is it generally sufficient to rely on the power provided by the Data Centre alone (which almost always claim UPS and power generators, don't they?), or are you supposed to have extra UPS within your own shelves?
Should the networking core be under its own UPS?
Does any major cloud or dedi provider have dedicated UPS units for each server/rack at all?