On Fri, Jul 8, 2016 at 12:23 PM, Jean-David Beyer <jeandav...@verizon.net> wrote:
> Why all this concern about how long a disk (or SSD) drive can stay up > after a power failure? > > It seems to me that anyone interested in maintaining an important > database would have suitable backup power on their entire systems, > including the disk drives, so they could coast over any power loss. > > I do not have any database that important, but my machine has an APC > Smart-UPS that has 2 1/2 hours of backup time with relatively new > batteries in it. It is so oversize because my previous computer used > much more power than this one does. And if my power company has a brown > out or black out of over 7 seconds, my natural gas fueled backup > generator picks up the load very quickly. > > Am I overlooking something? > Each added protection help, and cover some of the possible failure modes one may encounter. Most datacenters shouldn't lose power, and when they do, ups or equivalent systems should pick up, and then generators. Yet poweroffs happens. every element between the power source and the disk drives storing the database have chances of failure too. (including those two 'end' elements) Most servers shouldn't be powered off but it happens, alimentation cables may be moved, pdu may shutoff, electrical protections may trigger, someone may press one of the power buttons... Ideally you want protections on each level, or at least closest to the data (so that there are fewer potential elements to consider for failure cases) -- Thomas SAMSON
