To forestall that reply: I did think about it before hitting the reply button. I've seen a couple of large scale DC power outages in my 35 years of IT work. The vast majority of the hardware came through just fine. But older data centers with gear that has been running uninterrupted for many years tend to have at least some hardware that simply won't come up again, due to a variety of reasons. One can be that the on-board batteries have gone bad, which nobody noticed until the power cycle. Another is that some harddrives function well as long as they keep spinning but that has worn a nasty little spot on the bearing that keeps the spindle aloft. When it spins down, depending on the orientation it may not be able to start back up again, it may even crash while spinning down. Powercycle enough gear that has been running for years and you will most likely lose at least some small fraction of it. You could do it the next day after taking care of those and everything would likely be fine.