e77dbe04ac
We do not need these namespaces like xmlns:svg and xmlns:html anywhere, remove the declarations. Change-Id: Ic6aa62c28b2b21092d1e1d5c6f431807519f59af
31 lines
1.6 KiB
XML
31 lines
1.6 KiB
XML
<section xml:id="section_configure-backing-storage"
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xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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version="5.0">
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<title>Configure Compute backing storage</title>
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<para>Backing Storage is the storage used to provide
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the expanded operating system image, and any ephemeral storage.
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Inside the virtual machine, this is normally presented as two
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virtual hard disks (for example, /dev/vda and /dev/vdb respectively).
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However, inside OpenStack, this can be derived from one of three
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methods: LVM, QCOW or RAW, chosen using the
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<literal>libvirt_images_type</literal> option in <filename>nova.conf</filename>
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on the compute node.</para>
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<para>QCOW is the default backing store. It uses a copy-on-write philosophy to
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delay allocation of storage until it is actually needed. This means that the
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space required for the backing of an image can be significantly less on the real
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disk than what seems available in the virtual machine operating system.
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</para>
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<para>RAW creates files without any sort of file formatting, effectively creating
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files with the plain binary one would normally see on a real disk. This can
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increase performance, but means that the entire size of the virtual disk is
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reserved on the physical disk.
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</para>
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<para>Local <link xlink:href="http://http//en.wikipedia.org/wiki/Logical_Volume_Manager_(Linux)">LVM volumes</link>
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can also be used.
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Set <literal>libvirt_images_volume_group=nova_local</literal> where <literal>nova_local</literal> is the name
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of the LVM group you have created.
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</para>
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</section>
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