On Sat, Dec 29, 2007 at 08:02:12PM +0000, Dieter wrote:
> > But our power is down every 1~2 week.
> 
> Ouch.  A UPS will help, but even with a UPS you can get a hang/crash
> that corrupts data.  So a UPS is for riding through short outages,
> it is NOT a guarantee that the machine never goes down hard.


Well, if the spec is that the unit can be shutdown but needs to be
shutdown safely, then most COTS UPS will provide enough power to allow
an orderly shutdown of most COTS computers.  As long as the computer
gets the signal to shutdown in enough time before the UPS runs out of
juice.

Then again, most COTS UPS have batteries that, while called
maintenance-free, require maintenance in the form of replacment
periodically.  

If the spec is that the unit stay up during a power loss, then you need
something larger and probably with maintainable batteries.  I used to
live in the bush in Northern Ontario at the end of a 10 Km power line.
Every summer the power would fail once for at least 48 hrs and every
winter for about a week, in addition to frequent shorter outages.  As I
went to work during the day and my wife is disabled, I couldn't go with
a standard generator.  I went with a 3 KW inverter and 2000 Amp-hr
deep-cell battery.  It would power the necessities and the computer for
close to a week.  The inverter (Xantrex ProSine) produced a pure
sine-wave power with a virtually instantaneous switch-over that the
computer never noticed (neither did anything or anyone else).

Doug.