Re: Debian Compatable UPS?
On Sat, 08 Oct 2005, Alvin Oga wrote:
> and whether you agree or not is irrelevant to the original
> question of which one is debianize ..
Parse error.
> the answer is all ups will work if you have the magic wand ( skills )
This is incomplete. You also need magic powder (time and other resources),
which are often not of trivial cost. So this answer is at best useless.
> > Alvin's claim that they don't last long might be true, but here again, a
> > good db for Linux is lacking. How long is a UPS supposed to last?
His claim is right, batteries will last at most three years (do not expect
to get one that will last that much with any consumer or prosumer grade
UPS). UPS units can, and often last up to ten years (but not consumer grade
ones).
> > Then there are the prices. I would get an APC BP500UC, that's $110. But
> > Henrique reports on an APC Smartups, that's double the price, where I
> > look. So what is the price performance curve?
>
> how much is your server worth to you when the power is out
Actually, how much is the load (server and whatever else is there) worth.
An UPS can easily destroy the load in certan failure modes, and it does not
even require an input power loss to do that (although most of the time, such
failure modes happen while on battery and the battery either malfunctions or
is too close to being completely drained).
> HM> In my experience with other small UPS (< 10kVA) manufacturers, the
> HM> batteries often fail, but so does the control circuirty... and nearly
> HM> as often
>
> "good" control circuits should never fail on a "good" ups
Indeed. That's the reason I won't buy UPSes from these manufacturers ever
again.
> - it should last as long as the battery allows before it
> sends the shutdown signal to whatever its trying to protect
It needs to do this based on configurable parameters.
> - it should survive microsecond's of 40KV like lightening strikes
You will need power-utility-level surge supressors on the building primary
power distribution to survive a direct lightning hit of 40kV or more on the
wires.
The UPS cannot provide that, but it CAN provide enough surge suppresion to
protect the load and its control channel from surges induced by the lightning
EM-field in the internal wiring.
> HV> How can that be? If the software they provide to communicate over the
> HV> rs232 is m$ software?
>
> for you, get those silly usb-based ones that cmes with the m$ sw
Tut Tut, never give an anwer like that. Bad consultant!
Here is the way to buy an UPS for your home:
1. Know how much the load being protected is worth to you. And while at it,
seriously consider *insuring* the load against electrical damages.
2. Know how much the uptime of the load is worth to you (e.g. maybe it is
worth to keep it up for 5 minutes only, so that it will not notice fast
power cycles and do a clean shutdown on any real brownouts).
3. Know how much peak and maximum steady-state power the load needs (peak
power is often only important when dealing with non-delayed-start disk
arrays and laser-printing devices). When you buy the UPS, make sure the
load is at, or below 75% of the UPS maximum capacity.
Remember that kW and kVA are different things and you need to consider
both. For home devices you can probably just go with the kVA rating,
as long as you keep away from trying to drain >90% of the UPS maximum
rated capacity.
Now, choose the DFSG-software you will be using. If you have more than one
computer, or more than one UPS for a single computer, "nut" is probably the
best one.
Print out the compatibility chart of the software, and go shopping.
Alvin recommends not getting APC. I recommend not getting any unit below
1kVA from any manufacturer, and staying away from anything APC below a APC
SmartUPS XL. Certainly stay away from APC BackUPS, I have seen unnaceptable
failure modes described in some web forums (or if you get one, replace the
entire unit every two and a half years).
Actually, I suggest trying MGE UPSes, they are DFSG-friendly to the point of
supporting the development of DFSG UPS-monitor software (nut), and I could
not find a single complaint against their hardware through google... hmm, I
wonder if they have a Brazilian distributor already. DISCLAIMER: I have
never owned or tested a MGE UPS.
--
"One disk to rule them all, One disk to find them. One disk to bring
them all and in the darkness grind them. In the Land of Redmond
where the shadows lie." -- The Silicon Valley Tarot
Henrique Holschuh
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