On 07/02/2011 12:07 PM, Devin Reade wrote:
> There is one flaw that I know of with APC brand UPSes, although I wouldn't
> be surprised if other UPSes are similar (since APC has traditionally
> set the standard in the market): There is a small window between
> the time that the UPS initiates a shutdown and the control software
> (such as apcupsd) tells the UPS to kill power in (some number of) seconds.
> If your mains power returns and stays on during that window, your
> machine may not restart by itself: It may be too late to cancel the
> OS shutdown and subsequent power-off, but because the UPS still has
> mains power it doesn't trigger the power cycle that allows the computer
> to reboot (assuming you've configured your BIOS to boot at power-on).
> In my experience this doesn't happen often (I've seen it probably
> twice in 15 years), but it does happen and can be a real PITA if
> you don't have anyone on site that can deal with it.
Fix the shutdown sequence so that after killing the UPS, and right at the
point where you would tell the BIOS to turn off the ATX power supply, the
machine sleeps for a few seconds (longer than it should take for power to
drop) and then reboots instead of shutting down. If commercial power has
returned, you just reboot. If not, power is removed at a safe point.
--
Bob Nichols "NOSPAM" is really part of my email address.
Do NOT delete it.