OpenStack Glance: import images and convert them directly in Ceph

Ceph, to work in optimal circumstances requires the usage of RAW images. However, it is painful to upload RAW images in Glance because it takes a while. Let see how we can make our life easier.

First let’s upload our image, for the purpose of this example I used a tiny CirrOS image:

$ sudo rbd -p imajeez --image-format 2 import cirros-0.3.0-x86-64-disk.img.1 $(uuidgen)

$ sudo rbd -p imajeez info 33fc77e2-df0e-4f71-a966-b8df2b245f42
rbd image '33fc77e2-df0e-4f71-a966-b8df2b245f42':
  size 9532 kB in 3 objects
  order 22 (4096 kB objects)
  block_name_prefix: rbd_data.331574b0dc51
  format: 2
  features: layering

Now this is where it becomes interesting! The good thing here is that we can trigger the conversion directly from Ceph and this using the qemu-img tool. Prior to run the convertion make sure that your ceph.conf is configured to force the creation of images 2 format (rbd default format = 2). All the RBD images will be created using format 2 which supports layering (snapshot, clones etc…)/ Simply call a conversion and generate a new name based on a new UUID.

$ sudo qemu-img convert -O raw rbd:imajeez/33fc77e2-df0e-4f71-a966-b8df2b245f42 rbd:imajeez/$(uuidgen)

We now have two images in our pool:

$ sudo rbd -p imajeez ls
33fc77e2-df0e-4f71-a966-b8df2b245f42
4f460d8c-2af3-4041-a28d-12c3631a305f

And the image has a RAW format:

$ sudo qemu-img info rbd:imajeez/4f460d8c-2af3-4041-a28d-12c3631a305f
image: rbd:imajeez/4f460d8c-2af3-4041-a28d-12c3631a305f
file format: raw
virtual size: 39M (41126400 bytes)
disk size: unavailable
cluster_size: 4194304

We can now delete our original QCOW2 image:

$ sudo rbd -p imajeez rm 33fc77e2-df0e-4f71-a966-b8df2b245f42

In order for this image to be compliant with Glance, we need to snapshot and protect it:

$ sudo rbd --pool imajeez snap create --snap snap 4f460d8c-2af3-4041-a28d-12c3631a305f
$ sudo rbd --pool imajeez snap protect --image 4f460d8c-2af3-4041-a28d-12c3631a305f --snap snap

$ sudo rbd -p imajeez snap ls 4f460d8c-2af3-4041-a28d-12c3631a305f
SNAPID NAME     SIZE
     4 snap 40162 kB

Eventually add this image into Glance, note that using the --location flag will not upload anything since we directly register the location in Ceph.

$ glance image-create --id 4f460d8c-2af3-4041-a28d-12c3631a305f --name CirrosImport --store rbd --disk-format raw --container-format bare --location rbd://$(sudo ceph fsid)/imajeez/4f460d8c-2af3-4041-a28d-12c3631a305f/snap
+------------------+--------------------------------------+
| Property         | Value                                |
+------------------+--------------------------------------+
| checksum         | None                                 |
| container_format | bare                                 |
| created_at       | 2014-11-10T17:00:02                  |
| deleted          | False                                |
| deleted_at       | None                                 |
| disk_format      | raw                                  |
| id               | 4f460d8c-2af3-4041-a28d-12c3631a305f |
| is_public        | False                                |
| min_disk         | 0                                    |
| min_ram          | 0                                    |
| name             | CirrosImport                         |
| owner            | 2f314f86ca9048ac828baedb5e8e4e2a     |
| protected        | False                                |
| size             | 41126400                             |
| status           | active                               |
| updated_at       | 2014-11-10T17:00:02                  |
| virtual_size     | None                                 |
+------------------+--------------------------------------+

This procedure will probably be reproduced as soon as the Glance conversion blueprint gets implemented. As always, it’s easier with Ceph since we don’t need to store the image in a temporary location, convert it and then upload it. This is unfortunately the problem with backend such as Swift.