110 lines
7.6 KiB
HTML
110 lines
7.6 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta name="DC.Title" content="Decide what level of availability you need" />
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<meta name="abstract" content="After understanding availability at a basic level, it important to assess your individual availability needs. Higher availability is more costly than a lower level availability. You must balance your needs and services with the overall cost of implementing and maintaining these availability solutions." />
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<meta name="description" content="After understanding availability at a basic level, it important to assess your individual availability needs. Higher availability is more costly than a lower level availability. You must balance your needs and services with the overall cost of implementing and maintaining these availability solutions." />
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<meta name="DC.Relation" scheme="URI" content="rzalwoverview.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1998, 2006" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Decide what level of availability you need</title>
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</head>
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<body id="rzalwlevel"><a name="rzalwlevel"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Decide what level of availability you need</h1>
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<div><p><span><img src="./delta.gif" alt="Start of change" />After understanding availability at a basic level,
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it important to assess your individual availability needs. Higher availability
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is more costly than a lower level availability. You must balance your needs
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and services with the overall cost of implementing and maintaining these availability
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solutions.<img src="./deltaend.gif" alt="End of change" /></span></p>
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<p>You want to be sure that you have analyzed your business needs thoroughly
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in order to decide what level of availability you can afford to maintain.
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To decide what level of availability you need, consider the following questions:</p>
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<div class="section"><h4 class="sectiontitle">Do you have any applications that require 100% availability?</h4><p>In
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most cases, you can achieve a high level of availability by implementing sound
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processes and systems management practices. The closer you need to be to continuous
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availability, the more of an investment you have to make. Before you make
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that kind of investment, you should be sure that you require that level of
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availability. The following figure shows how different techniques can improve
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availability, but can increase the price you have to pay for it.</p>
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<div class="p"> <div class="fignone"><img src="rzalw501.gif" alt="Determine your level of availability" /></div>
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</div>
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<p><img src="./delta.gif" alt="Start of change" />If your requirements for levels of availability increase,
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you may want to consider multiple system availability solutions, such as clusters.<img src="./deltaend.gif" alt="End of change" /></p>
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</div>
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<div class="section"><h4 class="sectiontitle">How much downtime is acceptable to you?</h4><p>It may help
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you to know what amount of downtime each level of availability represents.
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The following table shows the amount of downtime you should expect for different
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levels of availability.</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="border" border="1" rules="all"><thead align="left"><tr><th valign="top" id="d0e37">Level of availability</th>
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<th valign="top" id="d0e39">Downtime per year</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" headers="d0e37 ">90%</td>
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<td valign="top" headers="d0e39 ">36.5 days</td>
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</tr>
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<tr><td valign="top" headers="d0e37 ">95%</td>
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<td valign="top" headers="d0e39 ">18.25 days</td>
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</tr>
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<tr><td valign="top" headers="d0e37 ">99%</td>
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<td valign="top" headers="d0e39 ">3.65 days</td>
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</tr>
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<tr><td valign="top" headers="d0e37 ">99.9%</td>
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<td valign="top" headers="d0e39 ">8.76 hours</td>
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</tr>
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<tr><td valign="top" headers="d0e37 "><img src="./delta.gif" alt="Start of change" />99.99%<img src="./deltaend.gif" alt="End of change" /></td>
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<td valign="top" headers="d0e39 "><img src="./delta.gif" alt="Start of change" />50 minutes<img src="./deltaend.gif" alt="End of change" /></td>
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</tr>
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<tr><td valign="top" headers="d0e37 "><img src="./delta.gif" alt="Start of change" />99.999%<img src="./deltaend.gif" alt="End of change" /></td>
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<td valign="top" headers="d0e39 "><img src="./delta.gif" alt="Start of change" />5 minutes<img src="./deltaend.gif" alt="End of change" /></td>
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</tr>
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</tbody>
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</table>
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</div>
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<p>Along with knowing how much downtime is acceptable to you, you
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need to consider how that downtime may occur. For example, you may think that
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99% availability is acceptable if the downtime is a series of shorter outages
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that are distributed over the course of a year. But, you may think differently
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about 99% availability if the downtime were actually a single outage that
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lasts 3 days.</p>
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<p><img src="./delta.gif" alt="Start of change" />You also need to consider when
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a downtime is acceptable and when it is not. For example, your average annual
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downtime goal per year might be 9 hours. If that downtime were to occur during
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critical business hours, it could have an adverse affect on the bottom line
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revenue for your company.<img src="./deltaend.gif" alt="End of change" /></p>
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</div>
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<div class="section"><h4 class="sectiontitle">What level of access do your customers need to your business?</h4><p><img src="./delta.gif" alt="Start of change" />It used to be that customers and business partners accessed your
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business from 9 a.m. to 5 p.m., so it was realistic to expect that your system
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only had to be available during those hours. However, the Internet and a diverse
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global marketplace have changed that expectation; customers and business associates
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may expect to have access to your company's data at any time of the day or
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night. Your working hours may be hours or even days different from your global
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business partner or customer. You have to determine what your customer expectations
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are, and what is realistic with regard to those expectations, as you determine
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what level of availability you will maintain.<img src="./deltaend.gif" alt="End of change" /></p>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzalwoverview.htm" title="In today's fast-paced Internet environment, it is crucial that your data and applications be available to you when you need them. If your customers cannot access your Web site because your system is down, they may go to your competitors instead.">Availability roadmap</a></div>
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</div>
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</div>
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</body>
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</html>
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