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Yasuhiro KIMURA
113 lines
4.9 KiB
HTML
113 lines
4.9 KiB
HTML
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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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>Using Recovery on Journaling Filesystems</title>
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<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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<link rel="start" href="index.html" title="Berkeley DB Programmer's Reference Guide" />
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<link rel="up" href="transapp.html" title="Chapter 11. Berkeley DB Transactional Data Store Applications" />
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<link rel="prev" href="transapp_hotfail.html" title="Hot failover" />
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<link rel="next" href="transapp_filesys.html" title="Recovery and filesystem operations" />
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</head>
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 18.1.40</p>
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</div>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">Using Recovery on Journaling Filesystems</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="transapp_hotfail.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 11. Berkeley DB Transactional Data Store Applications </th>
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<td width="20%" align="right"> <a accesskey="n" href="transapp_filesys.html">Next</a></td>
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</tr>
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</table>
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<hr />
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</div>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="transapp_journal"></a>Using Recovery on Journaling Filesystems</h2>
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</div>
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</div>
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</div>
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<p>
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In some cases, the use of meta-data only journaling file
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systems can lead to log file corruption. The window of
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vulnerability is quite small, but if the operating system
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experiences an unclean shutdown while Berkeley DB is creating
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a new log file, it is possible that upon file system recovery,
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the system will be in a state where the log file has been
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created, but its own meta-data has not.
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</p>
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<p>
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When a log file is corrupted to this degree, normal
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recovery can fail and your application may be unable to open
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your environment. Instead, an error something like this is
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issued when you attempt to run normal recovery on environment
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open:
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</p>
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<pre class="programlisting"> Ignoring log file: /var/dblog/log.0000000074: magic number
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6c73732f, not 40988
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Invalid log file: log.0000000074: Invalid argument
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PANIC: Invalid argument
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process-private: unable to find environment
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txn_checkpoint interface requires an environment configured for
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the transaction subsystem </pre>
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<p>
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In this case, it may be possible to successfully recover
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the environment by ignoring the log file that was being
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created — to do this, rename the log file with the
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highest number to a temporary name:
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</p>
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<pre class="programlisting"> mv DBHOME/log.000000XXX my-temporary-log-file </pre>
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<p>
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and try running normal environment recovery again. If
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recovery is successful, and your application is able to open
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the environment, then you can delete the log file that you
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renamed.
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</p>
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<p>
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If recovery is not successful, then you must perform a
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catastrophic recovery from a previous backup.
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</p>
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<p>
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This situation has been shown to occur when using ext3 in
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writeback mode, but other journaling filesystems could exhibit
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similar behavior.
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</p>
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<p>
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To be absolutely certain of your application's ability to
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recover your environment in the event of a system crash,
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either use non-journaling filesystems, or use a journaling
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filesystem in a safe (albeit slower) configuration, such as
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ext3 in ordered mode.
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</p>
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</div>
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<div class="navfooter">
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<hr />
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left"><a accesskey="p" href="transapp_hotfail.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="transapp.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="transapp_filesys.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">Hot failover </td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top"> Recovery and filesystem operations</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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