any good UPS for a Fedora server

[Rick Stevens]

On Wed, 2007-11-14 at 11:10 -0800, Dean S. Messing wrote:
> Bruno Wolff wrote:
> : > Saqib Ali wrote:
> : > I am looking for a UPS for a single Fedora server for a non-profit
> : > org. Only one machine (HP DL360 G4) will be connected to the UPS. We
> : > need about 2 hrs of run-time, with automatic shutdown capability, and
> : > restart when the power comes back.
> : > 
> : > Any good APC UPS that has rpm for Fedora?
> : 
> : For that long of a time you may want to look into some sort of backup
> : generator. You can get ones that run off natural gas for a few thousand
> : dollars.
> 
> A generator (with all the attendant noise, fumes, $$$$, &c.)  may be
> overkill if the machine is drawing less than a KW.  (I'm not familiar
> with the machine.)
> 
> You can go to GI Joe's (here in the U.S.A.) and buy a 1 KW
> 12V DC --> 120V AC inverter for $150.  You can then go to Sears
> and buy a "deep-charge" 12V  Rec. Vehicle battery for another $100 or so.
> This will give you a substantial (don't know exactly how much) number
> of minutes of high quality AC to run your computer.  Another N  $100 or
> so buys N more batteries which can be hooked in parallel to 
> multiply your original time by (N+1).
> 
> The only incomplete parts of this is the switch-over mechanism and the
> auto shutdown.  They make swithover devices for generators so the same
> device shd. be able to be used here, I suppose.

Having been down that road (and designed several datacenters), the
logical thing to do is to parallel the batteries to give you the
necessary run time, install a trickle charger on them and run the server
off the battery system all the time.  If you lose the mains, the
batteries keep feeding the system.  When the mains come back, the
charger recharges the batteries.  You don't need a cutover relay at all.

You do have to take care to ensure you get a charger big enough to
handle the number of batteries you've got in parallel (if the batteries
are dead there will be a pretty big surge current when they start
charging).  This is the basic design of all UPS systems.

The genset cutover systems typically switch the input supply to a UPS
between the mains and the genset--they do not switch the load.  In other
words, the computers run off the UPS all the time.  If there's a mains
outage, the cutover switch starts the genset, waits for it to stablize,
then switches the UPS' input from the mains to the genset.  The UPS
recharges/runs off the genset from there.  The computers don't know
anything about it as all they see is the UPS' output.

When main power returns, the cutover typically waits some period of time
to ensure the mains aren't going to poop out again, then switches the
UPS input back to the mains and shuts down the genset.  In all cases,
the UPS covers the switchover time.

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- Rick Stevens, Principal Engineer             rstevens at internap.com -
- CDN Systems, Internap, Inc.                http://www.internap.com -
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-    If your broker is so damned smart...why is he still working?    -
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