UPS backup musings

[acollins at icsmail.net]

Hi Graig.  The software you want is called apcupsd.  As a part of its
configuration, it let's you specify the amount of grace time before it
forces the system to do a graceful shut down when the ups battery is
getting low.  There are two types of ups hardware.  They either connect
via a serial port, or a usb cable.  The connection type is specified in
the config file.  When the software is started, it finds the connection
type in the config file, and then attemps to establish either a serial,
or a usb connection with the ups, depending on which connection type is
specified.  The ups comunicates with the software running on the
computer, informing it of the ups status, online, or running on battery.
 If it is running on battery, it also informs the software of how much
battery life is left.  When the ups gets to the grace time before a
shutdown is needed, it informs the software, which sends email to all
users on the system warning them to log off, because a system shutdown
is pending.  The config file is well commented, and the documentation is
very good.  Before you try to install the software or even buy a ups, I
strongly urge you to rtfm.  This is a project where you really want to
know what you are doing, and what you are looking for, before you buy ,
and install.  As a part of the manual, the softare has a list of makes
and models of upss that it supports.

The wattage of the ups controls how long the ups can power your system on
battery power.  The more hardware you plug in the the ups, the less time
it can provide power for everything that is connected.  A good unit will
be able to power your computer for two to 3 hours, or more, depending on
how good an ups you bought.  Usually, the higher the price, the more
battery life.

I hope this helps.

Gene Collins

>Hi all,
>this is primarily aimed at those here who have UPS (uninterruptable
>power supply) battery backup units. I seem to recall Kirk has one, and
>maybe others here do as well.
>
>We have a power outage here every 3-4 months, lasting anywhere from
>one second to close to 3 hours so far. So, I had been thinking of
>getting a UPS some day for a while now. According to my
>server/router's uptime, our most recent outage happened 36 days ago,
>and it lasted for a second, if not less. Everything including clock
>radios and stove clock seems to have survived it, except for the
>server. The fans and drive stayed on, but the machine was
>unresponsive, forcing me to power cycle it. That's when I decided that
>this happens frequently enough, and is annoying enough to maybe turn
>some day into in the near future.
>
>Until I researched UPS units, my idea of how they work was perhaps too
>idealistic. Power fails. Server properly shuts down. Power comes back
>on, server starts up. I found out though that this doesn't seem to be
>exactly how things go though.
>
>My server is setup in bios to turn on whenever power is applied. My
>research seems to indicate that there are two extremes as far as UPS
>units go. In the first extreme, power fails, the server shuts
>down. However, since the UPS isn't fully drained, the power from the
>UPS stays on, and the server doesn't start back up when the power
>company gets their act together, and utility power comes back
>on. That's fine if someone is around to press the power
>button. However, what if when this happens everyone here happens to be
>on a longer vacation?
>
>In the second extreme, some UPS units are set to cut power, and
>reapply power again about a minute after utility power comes back
>on. If the server shuts down before utility power comes back on,
>that's good. If utility power comes back on before the server shuts
>down, then the UPS causes the very problem it is supposed to
>prevent. This leads me to conclude that they're worth getting if one
>has a backup generator, or power outages tend to be short, and the UPS
>unit doesn't cycle the power.
>
>I also question the value of a proper shut down these days. Before
>journaling file systems, an improper shut down was a headache. Now
>though, it doesn't seem to be such a big deal. I've been through power
>failures maybe ten times now, and every time so far, the journals were
>recovered, and the system fully booted up, and was ready for prime
>time without my intervention (except in cases of split second
>outages). On the other hand, when we were having some electrical work
>done recently, I asked the electrician to wait for me to shut down
>the server before he cut the power, instead of just letting him cut
>power whenever he was ready.
>
>To keep this somewhat on topic, since the server only has USB ports,
>and no serial port, I was concerned about the compatibility of USB UPS
>units with gnu/linux. Based on reviews, the unit I would get if I
>decide to get it seems to be compatible with gnu/linux using USB to
>communicate:
>
>http://www.newegg.com/Product/Product.aspx?Item=N82E16842101311
>
>Finally, though not strictly necessary, I can't help thinking that it
>would be nice to power my dsl modem, network switch, wifi access
>point, server, and maybe charge other battery devices during a power
>outage for a while. I'm also wondering how hard it is to find
>replacement batteries locally or on-line? While I see UPS battery
>backup units on newegg, I haven't yet found a category with
>replacement batteries for them. The reviews seem to indicate that new
>batteries run for about $30 U.S., so that isn't bad, if I only knew
>I'd be able to find them in order to buy them.
>
>So for those of you who have these units, are they worth it, or are
>they maybe less valuable to have than in the past? Thanks for any
>comments.
>
>Greg
>
>
>-- 
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