openstack/openstack-manuals
Code Issues Proposed changes

Add note about config drive, backing storage

Browse Source 
From Grizzly, config drive is now supported well in Xen.

However, when using it, it is important to adjust the
 xenapi_disable_agent option, which this patch adds a note
about.

patchset2 adds a new config example snippet for backing storage

patchset3 addresses Diane's comments

patchset4 fixes syntax

fixes bug 1095506
fixes bug 1085404

Cherry-picked from https://review.openstack.org/35735

Change-Id: Ica515d3d2613d6b850bf7693715cc59dff73c5b4
This commit is contained in:
Tom Fifield
2013-07-05 14:22:32 +10:00
committed by Lorin Hochstein
parent 58bf57e8f6
commit bde138eeea
2 changed files with 39 additions and 1 deletions
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7
doc/src/docbkx/common/config-drive.xml
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@@ -30,7 +30,12 @@
>#1165174</link>). Make sure you install this program on each compute host
before attempting to use config drive, or an instance will not boot
properly.</para>
</note></para>
</note>
<note><para>
If you use Xen with a config drive, disable the agent through the
<literal>xenapi_disable_agent</literal> configuration parameter.
</para></note>
</para>
</simplesect>
<simplesect>
<title>Enabling the config drive</title>

33
doc/src/docbkx/openstack-config/compute-configure-backing-storage.xml Normal file
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@@ -0,0 +1,33 @@
<section xml:id="configuring-backing-storage"
xmlns="http://docbook.org/ns/docbook"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
xmlns:ns5="http://www.w3.org/1999/xhtml"
xmlns:ns4="http://www.w3.org/2000/svg"
xmlns:ns3="http://www.w3.org/1998/Math/MathML"
xmlns:ns="http://docbook.org/ns/docbook">
<title>Configuring Compute Backing Storage</title>
<para>Backing Storage is the storage used to provide
the expanded operating system image, and any ephemeral storage.
Inside the virtual machine, this is normally presented as two
virtual hard disks (eg /dev/vda and /dev/vdb respectively).
However, inside OpenStack, this can be derived from one of three
methods: LVM, QCOW or RAW, chosen using the
<literal>libvirt_images_type</literal> option in <literal>nova.conf</literal>
on the compute node.</para>
<para>QCOW is the default backing store. It uses a copy-on-write philosophy to
delay allocation of storage until it is actually needed. This means that the
space required for the backing of an image can be significantly less on the real
disk than what seems available in the virtual machine operating system.
</para>
<para>RAW creates files without any sort of file formatting, effectively creating
files with the plain binary one would normally see on a real disks. This can
increase performance, but means that the entire size of the virtual disk will be
reserved on the physical disk.
</para>
<para>Local <link xlink:href="http://http//en.wikipedia.org/wiki/Logical_Volume_Manager_(Linux)">LVM volumes</link>
can also be used.
Set <literal>libvirt_images_volume_group=nova_local</literal> where <literal>nova_local</literal> is the name
of the LVM group you have created.
</para>
</section>