UPS backup musings

[Kirk Reiser]

Hi Greg: I can't really give you an indepth discussion because
although I do have and use UPSs, I've never hooked up monitoring
software to take the systems down gracefully. When I was at the
university I had very large UPSs, here at the house I have a 1200 and
a 1500 watt units. They keep my equipment going for anywhere from five
minutes up to about 20 minutes. I have them powering four high end
servers, read that power suckers. I have the bios set to start in the
condition they were in when powered down, which works all right for my
needs. We don't tend to have really long outages unless a transformer
or substation goes down so most of the glitches only last a few
minutes at most. If I'm around when the units start beeping I start
taking them down by hand. If I'm not around they usually come up if
they went down when the power is restored.


On Thu, 13 Jun 2013, Gregory Nowak wrote:

> 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
>
>
>

-- 
Well that's it then, colour me gone!