mirror of https://github.com/tLDP/LDP
600 lines
28 KiB
XML
600 lines
28 KiB
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<?xml version="1.0"?>
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<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
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"http://docbook.org/xml/4.1.2/docbookx.dtd" [
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<!ENTITY howto "http://www.tldp.org/HOWTO/">
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<!ENTITY mini-howto "http://www.tldp.org/HOWTO/mini/">
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<!ENTITY home "http://www.catb.org/~esr/">
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]>
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<article id="index">
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<articleinfo>
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<title>UPS HOWTO</title>
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<author>
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<firstname>Eric</firstname>
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<othername>Steven</othername>
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<surname>Raymond</surname>
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<affiliation>
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<orgname><ulink url="&home;">Thyrsus Enterprises</ulink></orgname>
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</affiliation>
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</author>
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<revhistory>
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<revision>
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<revnumber>1.1</revnumber>
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<date>2004-02-21</date>
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<authorinitials>esr</authorinitials>
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<revremark>
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Add a little deployment advice, and stuff on other technologies.
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</revremark>
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</revision>
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<revision>
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<revnumber>1.0</revnumber>
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<date>2003-10-07</date>
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<authorinitials>esr</authorinitials>
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<revremark>
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Initial release.
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</revremark>
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</revision>
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</revhistory>
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<abstract><para>
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An Uninterruptible Power Supply (UPS) is an important thing to have
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if you live in an area where power outages are at all common,
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especially if you run a mail/DNS/Web server that must be up 24/7. This
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HOWTO will teach you things you need to know to select a UPS
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intelligently and make it work with your open-source operating system.
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</para>
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</abstract>
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</articleinfo>
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<sect1 id="introduction"><title>Introduction</title>
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<sect2 id="purpose"><title>Why this document?</title>
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<para>An Uninterruptible Power Supply (UPS) is an important thing to
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have if you live in an area where power outages are at all common,
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especially if you run a mail/DNS/Web server that must be up 24/7. The
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aging power grid in the U.S. has made this a more urgent issue than it
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used to be even for American hackers, but everyone is vulnerable to
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outages caused by storms and other natural phenoena. This document
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covers both the software and hardware aspects of protecting
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yourself.</para>
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<para>The advice in this document is aimed primarily at small
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installations — one computer and one UPS. Thus we'll focus on
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consumer-grade UPes, especially those designed for home and
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small-business use. If you are a data center administrator running a
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big server farm, there is a whole different (and much more expensive)
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range of technologies we'll do no more than hint at here.</para>
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</sect2>
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<sect2 id="newversions"><title>New versions of this document</title>
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<para>You can also view the latest version of this HOWTO on the World Wide Web
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via the URL <ulink url="&howto;UPS-HOWTO.html">
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&howto;UPS-HOWTO.html</ulink>.</para>
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</sect2>
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<sect2 id="license"><title>License and Copyright</title>
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<para>Copyright (c) 2003, Eric S. Raymond.</para>
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<para>Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.2
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
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A copy of the license is located at <ulink url="http://www.gnu.org/copyleft/fdl.html">www.gnu.org/copyleft/fdl.html</ulink>.</para>
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<para>Feel free to mail any questions or comments about this HOWTO to Eric
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S. Raymond, <email>esr@snark.thyrsus.com</email>. But please don't ask me
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to troubleshoot your general UPS problems; if you do, I'll just
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ignore you.</para>
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</sect2>
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</sect1>
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<sect1><title>An Overview of Power Protection</title>
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<para>There are three levels of power protection available to the
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home computer user. The levels are:</para>
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<orderedlist>
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<listitem><para>Surge Suppressor</para></listitem>
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<listitem><para>Line Conditioners</para></listitem>
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<listitem><para>Uninterruptible Power Supplies</para></listitem>
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</orderedlist>
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<para>While this HOWTO mainly focuses on UPSs, we'll start with some basics
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about the other two kinds of power filtering to help you understand where
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UPSes fit in. This is useful even though plummeting UPS prices have made
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the low-end alternatives less interesting than they used to be.</para>
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<sect2 id="surge"><title>Surge suppressors</title>
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<para>These are basically a fancy fuse between the source and your
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hardware; they clamp down spikes, but can't fill in a low voltage
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level or dropout.</para>
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<para>This is a bare minimum level of protection that any piece of
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expensive electronics should have. Note that this applies to more
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than just AC power; surge suppressors are available for (and should be
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used on) phone lines, and RS-232 and parallel connections (for use on
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long lines; generally not needed if the devices are colocated with the
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computer and all devices are protected from outside sources). Note
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also that <emphasis>all</emphasis> devices connected to your computer
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need to be protected; if you put a surge suppressor on your computer
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but not your printer, then a zap on the printer may take out the
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computer, too.</para>
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<para>An important fact about surge suppressors is that <emphasis>they
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need to be replaced if they absorb a large surge</emphasis>. Besides
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fuses, most suppressors rely on on components called Metal-Oxide
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Varistors (or MOVs) for spike suppression, which degrade when they
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take a voltage hit. The problem with cheap suppressors is that they
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don't tell you when the MOV is cooked, so you can end up with no spike
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protection and a false sense of security. Better ones have an
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indicator.</para>
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<para>You can buy surge suppressors at any Radio Shack; for better prices, go
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mail-order through Computer Shopper or some similar magazine. All of
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these are low-cost devices ($10-50).</para>
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</sect2>
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<sect2 id="conditioners"><title>Line Conditioners</title>
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<para>These devices filter noise out of AC lines. Noise can degrade
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your power supply and cause it to fail prematurely. They also protect
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against short voltage dropouts and include surge suppression.</para>
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<para>The Tripp-Lite 1200 I used to have was typical of the better class of
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line conditioners; a box with a good big soft-iron transformer and a couple
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of moby capacitors in it and <emphasis>no</emphasis> conductive path
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between the in and out sides. With one of these, you can laugh at
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brownouts and electrical storms. A fringe benefit is that if you
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accidentally pull your plug out of the wall you may find you actually have
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time to re-connect it before the machine notices (I did this once). But a
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true UPS is better.</para>
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<para>Netter Trey McLendon has good things to say about Zero Surge
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conditioners. He says: "Our systems at work [...] have been protected for
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2.5 years now through many a violent storm...one strike knocked [out] the
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MOV-type suppressors on a Mac dealer's training setup across the street
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from us. The Zero Surge just sort of buzzed when the surge came in, with
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no interruption whatsoever. The basic principle is this: ZS units slow
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down the surge with a network of passive elements and then sends it back
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out the neutral line, which is tied to ground <emphasis>outside at the
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box</emphasis> by code. MOV units shunt the surge to ground <emphasis>at
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the computer</emphasis>, where it leaps across serial ports, network
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connections, etc. doing its deadly work."</para>
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<para>Price vary widely, from $40-400, depending on the power rating
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and capabilities of the device. Mail-order from a reputable supply
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house is your best bet. Line conditioners typically
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<emphasis>don't</emphasis> need to be replaced after a surge; check to
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see if yours includes MOVs.</para>
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</sect2>
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<sect2><title>Uninterruptible Power Supplies</title>
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<para>The remainder of this document will focus on UPes. A UPS does three
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things for you. First, it filters the power your machine sees, smoothing
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out spikes and voltage fluctuations that can stress or even damage your
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electronics. Secondly, it provides a certain amount of dwell time in the
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event your power goes out entirely — this can often get you through
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brownouts and short blackouts. Third, when the UPS is about to run out of
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power it can arrange a graceful shutdown of your computer so that no
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unpleasant things happen to your disk filesystems. While the risks of
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unexpected shutdown are much lessened in these days of journalling
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filesystems like Linux's EXT3 or JFS from what they once were, ensuring a
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clean shutdown is still a valuable contribution to any system
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administrator's peace of mind.</para>
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</sect2>
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</sect1>
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<sect1><title>UPS Basics</title>
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<sect2><title>How To Select A UPS</title>
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<para>UPSes are nowadays very inexpensive. In the U.S. in 2003, quite
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capable ones are available for less than $150, and prices are heading
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down. In fact prices are so low now that we're not going to walk you through
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the elaborate optimization step that would have been important
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even two or three years ago, of estiming the watt dissipation of your
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computer and matching it to a UPS rating. Instead we'll explain
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why this would be a waste of effort and how to buy in a simpler
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and more effective way.</para>
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<para>UPSes are rated by the watts a full battery can put out before
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it drains. However, they are marketed using a VA (voltage-amps)
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figure; often, consumer-grade UPSes don't even specify a wattage on
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the box where you can see it. This is because the VA figure is larger
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and looks sexier. As a rule of thumb. assume the wattage is half of
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the VA rating; for an explanation of the complexities involved (if you
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care) see the white paper <ulink
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url='http://sturgeon.apcc.com/whitepapers.nsf/URL/WP-17/$FILE/WP17.pdf'>Understanding
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Power Factor, Crest Factor, and Surge Factor</ulink> on the APC
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website.</para>
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<para>But even if you know the watt rating of the UPS, it is the ratio of
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that figure with the wattage dissipation of your computer that
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controls the dwell time. Your dissipation is hard to predict; it can
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even be effected by things like the size of monitor you use (big ones
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can be quite power-hungry).</para>
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<para>Manufacturers try to get around this technical thicket by
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putting an expected dwell time on the box. But they exaggerate and
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even lie about their dwell times a lot (this is called
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<quote>marketing</quote>). What they'll do is quote you the dwell
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time you would get driving a bare minimum system with the disk drives
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shut off and a tiny monitor, in much the same way laptop manufacturers
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lie about their battery dwell times. The more honest UPS
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manufacturers give you a little table showing expected dwell times for
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different system configurations (<quote>desktop</quote>,
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<quote>tower</quote>, etc.). As a rule of thumb, assume you will get
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about 50% of the dwell time listed on the box for your configuration
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type.</para>
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<para>My advice is to forget the numbers game. Just go online or to
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your local computer store and buy one of the higher-end consumer or
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home-office models from APC, Best, Tripp-Lite, Belkin, or some other
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reputable manufacturer. Go ahead and grab the model with the longest
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dwell time, highest watt rating, or biggest VA number you can find;
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the premium for it is not likely to be more than $75 over the
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bargain-basement model. I guarantee you will feel very good about
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your decision not to pinch pennies come your first extended power
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outage.</para>
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<para>Perhaps a more compelling reason it is better to over-buy
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capacity rather than ending up with a UPS that is too weak for your
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power drain is that overstrained UPSes can fail in ugly ways,
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including <ulink
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url='http://www.exploits.org/nut/library/pictures/dead/'>catching fire
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and exploding</ulink>.</para>
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<para>Be sure you get a <firstterm>line interactive</firstterm> UPS
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rather than the older <firstterm>standby</firstterm> or
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<firstterm>SPS</firstterm> type. The older technology doesn't
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actually filter your power through the battery, so you're not assured
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of good voltage conditioning. The main advantage of an SPS (low cost)
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has been eroded now that line-interactive UPSes are so inexpensive.
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There are other UPS types, but they are either obsolescent or targeted
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at large data-center installations. For a detailed discussion of the
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different UPS types, see <ulink
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url='http://sturgeon.apcc.com/whitepapers.nsf/URL/WP-1/$FILE/WP1.pdf'>The
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different types of UPS systems</ulink>, a white paper on the APC
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site.</para>
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<para>Another important consideration is how your UPS will communicate
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with your computer. Do not buy a serial line UPS (one that
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communicates via an RS-232C cable). These are passing out of use in
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favor of UPS designs that use USB or Ethernet, for the very excellent
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reason that RS-232C interfaces are flaky, difficult to configure,
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and difficult to debug. Ethernet is overkill for this application;
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UPSes simply don't need that kind of bandwidth. We recommend sticking
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with USB, which is well-matched in price/performance to this job
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and relatively easy to troubleshoot.</para>
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<para>Until recently there was an important distinction between
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<firstterm>smart</firstterm> and <firstterm>dumb</firstterm> UPSes.
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Dumb UPSes did voltage-level signaling through individual pins; smart
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ones used the link as a primitive character channel and could pass
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more status information over it. But if you avoid RS232C UPSes you
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will never see a dumb one; indeed, it is likely that by the time you
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read this no dumb UPses will be in production any longer.</para>
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<para>Personally, I like APC UPSes (I have no connection with the
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company). But this is not the kind of widget for which manufacturer
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makes a whole lot of difference as long as you stick with one of
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the reputable brands.</para>
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</sect2>
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<sect2><title>Deploying your UPS and other devices: the total picture</title>
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<para>Our recommendation for a production Unix environment is a
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configuration like the following:</para>
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<orderedlist>
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<listitem><para>An UPS for the computer system. </para></listitem>
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<listitem><para>Surge suppression on all phone lines, and also on
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serial/parallel lines that leave the room.</para></listitem>
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<listitem><para>Line conditioners on any devices not connected to the UPS. If
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you do take a power hit, it's cheaper to replace a $50 line
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conditioner than a $1500 laser printer.</para></listitem>
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</orderedlist>
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<para>If this is too expensive for you, then downgrade the UPS to
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a line conditioner like the TrippLite. But don't go without at least
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that. Running unprotected is false economy, because you
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<emphasis>will</emphasis> lose equipment to electrical storms —
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and, Murphy's Law being what it is, you will always get hit at the
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worst possible time.</para>
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<para>One thing to note is that you typically shouldn't put a
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laser printer on a UPS — toner heaters draw enough current to
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overload a UPS and cause a shutdown within seconds. The other thing
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is that you can't even put the laser printer on the same circuit with
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a UPS — the heater kicks on every 20-30 seconds, and most UPSs
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will see the current draw as a brownout. So buy a separate line
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conditioner for the laser printer.</para>
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<para>A UPS should be wired directly to (or plugged directly into) the
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AC supply (i.e. a surge suppressor is neither required nor suggested
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between the wall and the UPS). In addition, a surge suppressor
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between the UPS and the equipment connected to it is redundant.</para>
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</sect2>
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<sect2><title>Software Assistance</title>
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<para>Your UPS communicates with your computer so it can gracefully
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shut the computer down when an outage has lasted too long for the
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battery to cope. In order for graceful shutdown to actually happen,
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your computer needs to have a background process — a daemon, in
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Unix terms — watching whatever messages come over the UPS cable
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for the one that says <firstterm>terminate</firstterm>. Then it
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needs to tell the operating system to shut down.</para>
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<para>Your UPS probably comes with a CD full of such software. Throw
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it away, as (a) most of it will be useless bits written for Windows
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systems, and (b) in the unlikely event you get Linux software it will
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almost certainly be stale binaries for a version you don't run.</para>
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<para>Back in the days of dumb serial-line UPses, there used to be
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about half a dozen different open-source UPS monitor daemons:
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<application>apcd</application>, <application>dumbupsd</application>,
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<application>genpowerd</application>.
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<application>powerd</application>, <application>smupsd</application>,
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<application>usvd</application> and more. These were fairly stupid
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programs for a simple job. Many required you to hand-wire a custom
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RS232C cable to get around various evil things that UPS manufacturers
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did to their ports in order to lock in customers.</para>
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<para>Those days are gone. USB UPSes get rid of the cable-hacking and
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hardware klugery, but require a bit more smarts from a monitor daemon.
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Accordingly the field has narrowed considerably. There appear
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to be only two such projects left standing.</para>
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<para>The <ulink url='http://www.exploits.org/nut/'>Network UPS
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Tools</ulink> project is a generic UPS monitor daemon that aims to
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communicate intelligently with all current UPS designs.</para>
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<para><ulink url='http://www2.apcupsd.com/'>apcupsd</ulink> is a daemon
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specifically designed for communicating with UPSes made by APC, the
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American Power Corporation.</para>
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<para>Both are solid, well-run projects. Their development groups are
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mutually friendly, and there has been occasional talk of a merger.
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Awkwardly, as of October 2003 the <application>apcupsd</application>
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project is the more featureful of the two, with, among other things,
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better USB support and better documentation — but the NUT tools
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have a cleaner architecture, more developers, and acceptance in Red Hat
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and other major distributions.</para>
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<para>My advice is simple; run <application>apcupsd</application> if
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you buy an APC UPS, and the NUT tools if you buy anything else. RPMs
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and Debian packages (which will modify your system's boot sequence
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appropriately as well as installing the daemon binaries) are available
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for both, so installation should be easy either way.</para>
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</sect2>
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<sect2><title>Preparing Your System For Auto-Reboot</title>
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<para>If you are using your UPS to try to keep a DNS/Web/mailserver up
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24/7, you will want to make sure the machine can be configured to
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boot automatically when it is powered up.</para>
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<para>This is not the normal behavior of most computers as shipped
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from the factory. Normally after the power is cut and restored, you
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must explicitly press a button for the power to actually be turned
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on. You can test your computer by powering it down; shutting off the
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power (pull the plug); then plugging the cord back in. If your
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computer immediately starts up, good. There is nothing more to
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do.</para>
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<para>If your computer does not start up, manually turn on the
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power (by pressing the power on button) and enter your computer's
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SETUP program (often by pressing DEL during the power up sequence;
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sometimes by pressing F10). You must then find and change the
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appropriate configuration parameter to permit instant power
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on.</para>
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<para>Normally, this is located under the <emphasis
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role="bold">BOOT</emphasis> menu item, and will be called something
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such as <emphasis role="bold">Restore on AC/Power Loss</emphasis> or
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<emphasis role="bold">Full-On</emphasis>. The exact words will vary
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according to the ROM BIOS provider. Generally you will have three
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options: <emphasis role="bold">Last State</emphasis>, <emphasis
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role="bold">Power On</emphasis>, and <emphasis role="bold">Power
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Off</emphasis>.</para>
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<para>Some BIOSes do not support such an option. This is idiotically
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bad design, but it does happen. If so, your only practical remedy is
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to get a new motherboard.</para>
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</sect2>
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</sect1>
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<sect1 id='maintaining'><title>Maintaining Your UPS</title>
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|
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<para>Your UPS has a battery inside it. Usually it is a lead-acid
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type (those are the least expensive for the manufacturer), but both
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lithium and gel-cel batteries are sometimes used.</para>
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<para>The battery is by far the most vulnerable and failure-prone part
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of your UPS. If you have your UPS long enough, you will probably have
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battery problems. Once every six months to a year or so you should
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recalibrate your UPS's battery sensor, and once every several years
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you will have to replace the batteries.</para>
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<sect2><title>Extending battery life</title>
|
|
|
|
<para>To extend your battery life, (a) avoid deep discharges, and (b)
|
|
don't expose them to extremes of heat, cold, or humidity.
|
|
Unfortunately there is not much you can do to avoid deep-discharging
|
|
your UPS other than living in an area where power outages are few
|
|
and short.</para>
|
|
|
|
</sect2>
|
|
<sect2><title>Recalibrating Your UPS</title>
|
|
|
|
<para>Your UPS's dwell-time calibration will lose accuracy over the life
|
|
of the battery. The usual symptom of this problem is that the UPS
|
|
overestimates the dwell time it has remaining during outages, but
|
|
occasionally it can also lead to an actual bad-battery condition going
|
|
undetected and very odd symptoms as a result.</para>
|
|
|
|
<para>UPSes have a recalibration procedure built into their firmware.
|
|
It generally involves deep-discharching and recharging the battery
|
|
while the UPS is in a special test mode. Your recipe for triggering
|
|
such a recalibration will vary according to your UPS software.</para>
|
|
|
|
<para>You always need to do this when you install new batteries (see
|
|
below). It is a good idea to do it once every six to twelve months
|
|
as routine maintenance, but no more often than that; as we noted
|
|
previously, deep discharges shorten your battery life.</para>
|
|
</sect2>
|
|
|
|
<sect2><title>Replacing Your Batteries</title>
|
|
|
|
<para>All modern UPSes have a low-battery alarm and run a periodic
|
|
self-test; they will alert you when replacement is needed. Usually
|
|
they both flash an indicator and make an alarm sound. If you have a
|
|
monitoring daemon set up, they will alert it and you will probably get
|
|
warning mail. If you ignore the alarm it will time out, but be
|
|
repeated at intervals.</para>
|
|
|
|
<para>You will occasionally get a false alarm. It's a good idea, if you
|
|
get an alarm, to explicitly trigger a UPS self-test the next day and see if
|
|
the alarm goes away (the procedure for doing this varies depending on
|
|
your UPS software). If the alarm is persistent, you need to replace
|
|
the batteries.</para>
|
|
|
|
<para>It has been reported that bad batteries can also produce symptoms
|
|
that mimic inverter failures or wonky control electronics. Even if
|
|
your UPS is displaying epileptic symptoms like repeating alarms and
|
|
flashing panel lights, a bad battery is the first thing to
|
|
suspect.</para>
|
|
|
|
<para>UPS manufacturers would of course prefer that you replace your
|
|
entire UPS when the batteries die, since they make more money that
|
|
way. But in fact there is nothing unique or magic about UPS batteries.
|
|
They are standard types also used for other applications such as
|
|
powering marine electronics, with standard connectors. You can buy
|
|
them from sources other than the UPS manufacturer, and sometimes replace
|
|
them with equivalents that are better and less expensive.</para>
|
|
|
|
<para>It's best to wait until the low battery alarm before ordering a
|
|
replacement; keeping batteries on the shelf reduces their life unless
|
|
you keep them fully charged.</para>
|
|
|
|
<para>Do not throw old batteries in your regular trash! They contain
|
|
toxic metals and acids. Be kind to your environment and hand them to
|
|
a qualified party for recycling. Most battery dealers will cheerfully
|
|
do this for you. If not, your local garbage company or waste-disposal
|
|
authority can explain to you how and where to turn them in
|
|
safely.</para>
|
|
|
|
<para>Below, you will find some suggestions for buying replacement
|
|
batteries. One <emphasis>important</emphasis> note of caution: at
|
|
least one user purchased one of the aftermarket batteries noted below
|
|
and found out that they would not fit into his unit. This required
|
|
cutting and soldering and other very undesirable things, so be
|
|
extremely careful in measuring your batteries — including every
|
|
millimeter of the terminal connections, which can cause
|
|
problems.</para>
|
|
|
|
<para>Although you can do a hot swap of your batteries while the
|
|
computer is running, it may not be very satisfactory, because the unit
|
|
will not know that the batteries have been swapped and your monitor
|
|
daemon will continue to show a low-battery indication. To correct
|
|
this situation, you must do a discharge and recharge of the
|
|
battery. At that point the battery should be calibrated better.</para>
|
|
|
|
<para>It may take several discharges and recharges of new batteries
|
|
before they reach full capacity and the dwell-time calibration is
|
|
accurate. If your UPS contains two or more battery units and your
|
|
monitoring software reports separate voltage levels for them, one way
|
|
to tell is to watch the divergence in voltage levels. As the cells
|
|
reach nominal full capacity, their voltages should converge.</para>
|
|
|
|
</sect2>
|
|
<sect2><title>Buying Batteries</title>
|
|
|
|
<para>APC makes "Replacement Battery Units" for each of the
|
|
SmartUPS models, but they sell them directly only in the U.S. Your
|
|
local Yamaha SeaDoo shop (if you have one) carries 35 ampere-hour deep
|
|
cycle marine batteries that are direct replacements for the kind APC
|
|
uses in many of its models. These are gel-cel and will double the
|
|
runtime and/or cut your recharge time in half. Here are some West
|
|
Coast sources:</para>
|
|
|
|
<programlisting>
|
|
Jet Works
|
|
1587 Monrovia Ave.
|
|
Newport Beach CA 9266?
|
|
Tel: +1 714 548-5259
|
|
|
|
J-W Batteries, Inc.
|
|
Tel: +1 714 548-4017
|
|
|
|
WPS 49-1200
|
|
GEL-CELL KB-35 BATTERY
|
|
</programlisting>
|
|
|
|
<para>The company I've heard most strongly recommended (by Carl
|
|
Erhorn, a core developer on the <application>apcupsd</application>
|
|
project) is called Battery Wholesale Distributors of Georgetown,
|
|
Texas. If you have questions, you can reach them by phone at (800)
|
|
365-8444, 9:00AM to 5:00PM (their local time), Monday through
|
|
Friday. Carl reports having gotten email from them on the weekends,
|
|
although the office is not open then.</para>
|
|
|
|
<para>The web site, with current pricing, is <ulink
|
|
url="http://www.batterywholesale.com">www.batterywholesale.com</ulink>.
|
|
They will ship outside of the US, they take all the usual credit
|
|
cards, and they accept orders by phone or Web.</para>
|
|
|
|
<para>Carl reports that BWD has found manufacturers who make batteries
|
|
in the standard case sizes, but have additional capacity over original
|
|
UPS batteries. Often, the difference is as much as 15% or so, and this
|
|
can result in additional runtime. It's a nice upgrade for a minor
|
|
increase in price.</para>
|
|
|
|
<para>BWD is also 'green-aware', in that they encourage you to
|
|
recycle your old batteries, and will accept the old batteries back
|
|
from you if you cannot find a local place that recycles them. You
|
|
pay the shipping but other than that, there is no charge.</para>
|
|
|
|
<para>Carl says <quote>I've been very pleased with their
|
|
products, service, and pricing. I hope you find them as helpful to
|
|
you as I do. I've been dealing with them since about 1994, and have
|
|
never been disappointed. The owner of the place also is very good
|
|
on technical issues, so if you have questions on their products, he
|
|
can get as technical as you need to go.</quote></para>
|
|
</sect2>
|
|
</sect1>
|
|
<sect1><title>Acknowledgements and Related Resources</title>
|
|
|
|
<para>Substantial portions of this document, notably the bits on
|
|
maintaining your UPS, were originally part of the
|
|
<application>apcupsd</application> documentation. The project
|
|
maintainers have graciously permitted me to re-use them here. Other
|
|
parts were part of my <ulink url='&howto;/Unix-Hardware-Buyer-HOWTO/'>Unix
|
|
Hardware Buyer HOWTO</ulink>.</para>
|
|
|
|
<para>There was a previous UPS HOWTO by Harvey J. Stein, last updated
|
|
in 1997. It was so out of date that I ended up using none of it.</para>
|
|
|
|
<para>There is <ulink
|
|
url='http://www.jetcafe.org/~npc/doc/ups-faq.html'>UPS FAQ</ulink>
|
|
which is slightly dated but still contains some good advice.</para>
|
|
|
|
</sect1>
|
|
</article>
|
|
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