185 lines
8.3 KiB
HTML
185 lines
8.3 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<head>
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<meta http-equiv="content-type" content="text/html; charset=UTF-8">
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<title>Archiving error correction files</title>
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<link rel="stylesheet" type="text/css" href="../include/dvdisaster.css">
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</head>
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<body>
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<!-- Title header -->
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<table width="100%" cellpadding="0" border="0">
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<tr>
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<td align="left">
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<span class="fxxl"><b>dvdisaster</b></span>
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<i>Version 0.72.4 / 0.72 (pl4)</i>
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</td>
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<td align="right">
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<span class="fxxl"> </span><a href="http://dvdisaster.net/en/">To the Internet version</a>
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<a href="../cs/howtos24.html"></a>
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<a href="../de/howtos24.html"></a>
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<a href="../ru/howtos24.html"></a>
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<table width="100%" cellpadding="0" border="0">
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<tr><td colspan="2" style="height: 10px">
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</table>
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<table width="100%" cellspacing=0>
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<td style="background-color:#f0f0f0; vertical-align:top; width:20%;">
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<table width="100%" cellpadding="10">
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<tr>
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<td>
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<span class="fs"><b>Contents</b></span>
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<table width="100%" cellpadding="0" cellspacing="0">
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<tr>
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<td class="hsep"></td>
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</tr>
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</table><p>
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<table width="100%">
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<tr><td colspan=3><span class="fs"><a href="news.html">News</a></span></td></tr>
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<tr><td></td><td></td><td style="height:10px;"></td></tr>
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<tr><td colspan=3><span class="fs"><a href="index.html">Overview</a></span></td></tr>
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<tr><td></td><td></td><td style="height:10px;"></td></tr>
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<tr><td colspan=3><span class="fs"><a href="howtos.html">Howtos</a></span></td></tr>
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<tr><td style="width:1%; vertical-align:top;">·</td><td colspan=2><span class="fs"><a href="howtos60.html">The big picture</a></span></td></tr>
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<tr><td style="width:1%; vertical-align:top;">·</td><td colspan=2><span class="fs"><a href="howtos10.html">Scanning media for errors</a></span></td></tr>
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<tr><td style="width:1%; vertical-align:top;">·</td><td colspan=2><span class="fs"><a href="howtos20.html">Putting error correction data on a separate file</a></span></td></tr>
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<tr><td></td><td style="vertical-align:top; font-size:small;">-</td><td><span class="fs"><a href="howtos21.html">Decision help</a></span></td></tr>
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<tr><td></td><td style="vertical-align:top; font-size:small;">-</td><td><span class="fs"><a href="howtos22.html">Basic settings for reading</a></span></td></tr>
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<tr><td></td><td style="vertical-align:top; font-size:small;">-</td><td><span class="fs"><a href="howtos23.html">Creating the error correction file</a></span></td></tr>
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<tr><td></td><td style="vertical-align:top; font-size:small;">-</td><td><span class="fs">Archiving error correction files</span></td></tr>
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<tr><td></td><td style="vertical-align:top; font-size:small;">-</td><td><span class="fs"><a href="howtos25.html">Advanced settings</a></span></td></tr>
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<tr><td style="width:1%; vertical-align:top;">·</td><td colspan=2><span class="fs"><a href="howtos30.html">Putting error correction data on the medium</a></span></td></tr>
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<tr><td style="width:1%; vertical-align:top;">·</td><td colspan=2><span class="fs"><a href="howtos40.html">Recovering media images</a></span></td></tr>
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<tr><td style="width:1%; vertical-align:top;">·</td><td colspan=2><span class="fs"><a href="howtos50.html">Getting information about images and error correction data</a></span></td></tr>
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<tr><td style="width:1%; vertical-align:top;">·</td><td colspan=2><span class="fs"><a href="howtos90.html">Testing image compatibility</a></span></td></tr>
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<tr><td style="width:1%; vertical-align:top;">·</td><td colspan=2><span class="fs"><a href="howtosa0.html">Dialogs and buttons</a></span></td></tr>
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<tr><td></td><td></td><td style="height:10px;"></td></tr>
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<tr><td colspan=3><span class="fs"><a href="download.html">Download</a></span></td></tr>
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<tr><td></td><td></td><td style="height:10px;"></td></tr>
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<tr><td colspan=3><span class="fs"><a href="qa.html">Questions and Answers</a></span></td></tr>
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<tr><td></td><td></td><td style="height:10px;"></td></tr>
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<tr><td colspan=3><span class="fs"><a href="feedback.html">Bug reporting</a></span></td></tr>
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</table>
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</td>
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</tr>
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</table>
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</td>
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<td></td>
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<!-- Actual page contents -->
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<td style="vertical-align:top; width:77%;" rowspan="2">
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<table width="100%" style="background-color:#f0f0f0;">
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<tr><td><span class="fl"><b>Creating error correction files</b></span></td>
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<td rowspan="2" align="right"><img src="images/create-icon.png" alt=""></td></tr>
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<tr><td><i>Archival</i></td></tr>
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</table><p>
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<!-- Insert actual page content below -->
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<h3 class="top">Tips for archival of error correction files</h3>
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CD/DVD/BD are currently among the most cost-effective exchangeable
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mass storage media. Therefore you are probably considering them
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for storing error correction files.<p>
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Nothing is wrong with doing so, but be aware that your data and protective
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error correction files are kept on media with equal reliability.
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When you encounter read errors on a data medium
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it is likely that the medium containing the respective error correction files
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has also gone defective. After all both media have been written at the same time,
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and they have the same aging characteristics.
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<p>
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<table width="100%"><tr><td class="vsep"></td>
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<td> </td>
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<td>This might come at a surprise, but it can not be guaranteed that an
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error correction file remains usable when it is stored on a defective medium -
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here is a <a href="qa32.html#file">explanation of the technical background</a>.
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</td></tr></table><p>
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Therefore it is important to protect error correction files just as if
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they were normal data. To be more specific,
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the medium containing error correction files must be protected with
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error correction data as well. Here are two ways of doing this:
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<ol>
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<li>Storing error correction files on separate media:<p>
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Use additional media just for keeping the error correction files.
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If you use no more than 80% per medium for error correction files
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it can
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be <a href="howtos30.html">augmented with error correction data</a>.
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This allows you to recover the medium if you run into problems
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reading the error correction files at a later time.<p></li>
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<li>Storing error correction files on the next medium in sequence:<p>
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Maybe you are using media for an incremental backup strategy. In that
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case you could collect files until the first medium can be filled.
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Write that medium as usual and create an error correction file for it.
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Include that error correction file into the backup set which will go
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onto the second medium. When the second medium has been written, write
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the error correction file for it onto the third medium and so on.
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This way all media in the chain are protected with error correction
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files (with the ecc file for the last medium residing on hard disk until
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another medium is written).<p>
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Of course Murphys Law may strike and result in all media of the chain
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becoming defective. In that case you need to recover all media, starting
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with the most recent one ;-)
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</li>
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</ol>
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<!-- do not change below -->
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</td> <!-- end of page contents -->
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</tr>
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<tr><td colspan="2" class="hsep"></td>
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</tr>
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<tr>
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<td align="center">
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<span class="fs">
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<i> Copyright 2004-2012 Carsten Gnörlich.<br>
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Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved.
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</i>
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</span>
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</td>
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<tr><td colspan="2" class="hsep"></td>
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</body>
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</html>
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