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Introduce some basic docs describing the virtlockd setup. Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
49 lines
1.9 KiB
XML
49 lines
1.9 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<body>
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<h1>Virtual machine lock manager</h1>
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<ul id="toc"></ul>
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<p>
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Libvirt includes a framework for ensuring mutual exclusion
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between virtual machines using host resources. Typically
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this is used to prevent two VM processes from having concurrent
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write access to the same disk image, as this would result in
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data corruption if the guest was not using a cluster
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aware filesystem.
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</p>
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<h2><a name="plugins">Lock manager plugins</a></h2>
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<p>
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The lock manager framework has a pluggable architecture,
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to allow different locking technologies to be used.
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</p>
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<dl>
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<dt>nop</dt>
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<dd>This is a "no op" implementation which does absolutely
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nothing. This can be used if mutual exclusion between
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virtual machines is not required, or if it is being
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solved at another level in the management stack.</dd>
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<dt><a href="locking-lockd.html">lockd</a></dt>
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<dd>This is the current preferred implementation shipped
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with libvirt. It uses the <code>virtlockd</code> daemon
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to manage locks using the POSIX fcntl() advisory locking
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capability. As such it requires a shared filesystem of
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some kind be accessible to all hosts which share the
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same image storage.</dd>
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<dt><a href="locking-sanlock.html">sanlock</a></dt>
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<dd>This is an alternative implementation preferred by
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the oVirt project. It uses a disk paxos algorithm for
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maintaining continuously renewed leases. In the default
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setup it requires some shared filesystem, but it is
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possible to use it in a manual mode where the management
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application creates leases in SAN storage volumes.
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</dd>
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</dl>
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</body>
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</html>
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