Document VMs with disks stored in LVM

[Lorin Hochstein]

Document new Compute feature to support using LVM block devices for local storage for QEMU-based hypervisors.

Blueprint: https://blueprints.launchpad.net/nova/+spec/lvm-disk-images

Commit that introduced the feature: https://github.com/openstack/nova/commit/e0540dfed1c1276106105aea8d5765356961ef3d

New flags:
 * libvirt_images_type
 * libvirt_images_volume_group
 * libvirt_sparse_logical_volumes

This should be documented in the Compute Admin guide.

We should also document whether it's possible to do snapshots with this image format, since there was a question about this on the mailing list.

[Tom Fifield (fifieldt)]

It would be great to get this new feature written up pre folsom release.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/12984

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/12984
Committed: http://github.com/openstack/openstack-manuals/commit/df7b399292a8cddddd3c6ab227c96c3c7c03cdf3
Submitter: Jenkins
Branch: master

commit df7b399292a8cddddd3c6ab227c96c3c7c03cdf3
Author: Boris Filippov <email address hidden>
Date: Fri Sep 14 00:47:07 2012 +0400

    Document VMs with disks stored in LVM

    Add description for options related to feature of LVM backed
    instances in libvirt driver. Explicitly specify, that current
    implementation of snapshotting works only with Qcow2 backed instances.

    This resolves bug 1027606

    Change-Id: Idef54b27478026760cb99131ea1bc21f5ee53afc