[Ceph][Cinder] Cinder to boot a VM using a copy-on-write clone of an image

[Ivan Kolodyazhny]

According to [1], to create volume from image if Ceph is backend both for Cinder and glance, we have to use images in raw format. If images are stored in qcow format, Cinder will convert it to raw: it's very slow operation to download N GB image, convert it and upload to Ceph again. We have to add this note to our documentation.

For MOS <9.0 we also should mention in the documentation that we recommend set the following options in configs on all controllers:

glance.conf
show_image_direct_url = False

cinder.conf:
glance_api_version = 2

Also, you have to restart both cinder-api and glance-api services using following commands:
# service glance-api restart
# service cinder-api restart

[1] http://docs.ceph.com/docs/master/rbd/rbd-openstack/

Also, we have to recommend use only 'raw' image format for Ceph

[Bug Checker Bot (bug-checker)]

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[Fuel Devops McRobotson (fuel-devops-robot)]

Fix proposed to branch: master
Change author: Svetlana Karslioglu <email address hidden>
Review: https://review.fuel-infra.org/20956

[Fuel Devops McRobotson (fuel-devops-robot)]

Reviewed: https://review.fuel-infra.org/20956
Submitter: Michele Fagan <email address hidden>
Branch: master

Commit: 145c8d7cd92bddf30642681e68d9d4f4c9372fbe
Author: Svetlana Karslioglu <email address hidden>
Date: Wed May 25 17:32:25 2016

Update the Ceph Best Practices Guide

- Added the 2.4 Configure the Imaging and Block Storage services for Ceph
  section.
- Added the following text in 2.1 Ceph and OpenStack integration:

  ``You can use Ceph as a back end for Glance and Cinder. However, in this
    case you need to upload images to Glance in .raw format.``

Change-Id: I8dd09fa9fbe9579eef024a28e2f7a1558a47df0c
Closes-bug: 1568898

[Denis Meltsaykin (dmeltsaykin)]

Moving to Won't Fix for 6.1/7.0/8.0 since the change is already in the Ceph Best practices guide.