On Fri, Jul 8, 2016 at 12:23 PM, Jean-David Beyer <jeandavid8@xxxxxxxxxxx> 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
