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52 lines
2.8 KiB
XML
52 lines
2.8 KiB
XML
<?xml version="1.0"?>
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<h1>Terminology and goals</h1>
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<p>To avoid ambiguity about the terms used, here are the definitions
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for some of the specific concepts used in libvirt documentation:</p>
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<ul>
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<li>a <strong>node</strong> is a single physical machine</li>
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<li>an <strong>hypervisor</strong> is a layer of software allowing to
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virtualize a node in a set of virtual machines with possibly different
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configurations than the node itself</li>
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<li>a <strong>domain</strong> is an instance of an operating system
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(or subsystem in the case of container virtualization) running on a
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virtualized machine provided by the hypervisor</li>
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</ul>
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<p class="image">
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<img alt="Hypervisor and domains running on a node" src="node.gif"/>
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</p>
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<p>Now we can define the goal of libvirt: to provide a common generic
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and stable layer to securely manage domains on a node. The node may be
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distant and libvirt should provide all APIs needed to provision, create,
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modify, monitor, control, migrate and stop the domains, within the limits
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of the support of the hypervisor for those operations. Multiple nodes may
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be accessed with libvirt simultaneously but the APIs are limited to
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single node operations.</p>
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<p>This implies the following sub-goals:</p>
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<ul>
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<li>the API should not be targeted to a single virtualization environment
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which also means that some very specific capabilities which are not generic
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enough may not be provided as libvirt APIs</li>
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<li>the API should allow to do efficiently and cleanly all the operations
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needed to manage domains on a node</li>
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<li>the API will not try to provide high level virtualization policies or
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multi-nodes management features like load balancing, but the API should be
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sufficient so they can be implemented on top of libvirt</li>
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<li>stability of the API is a big concern, libvirt should isolate
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applications from the frequent changes expected at the lower level of the
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virtualization framework</li>
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<li>the node being managed may be on a different physical machine than
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the management program using libvirt, to this effect libvirt supports
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remote access, but should only do so by using secure protocols.</li>
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<li>libvirt will provide APIs to enumerate, monitor and use the resources
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available on the managed node, including CPUs, memory, storage, networking,
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and NUMA partitions.</li>
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</ul>
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<p>So libvirt is intended to be a building block for higher level
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management tools and for applications focusing on virtualization of a
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single node (the only exception being domain migration between node
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capabilities which involves more than one node).</p>
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</body>
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</html>
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