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How to take snapshot of VM which is booted from volume??

asked 2018-10-08 07:31:02 -0500

vathanlal gravatar image

updated 2018-10-09 03:36:17 -0500

Hello All,

In my OpenStack cluster(Newton) I have VM's which are booted from volume(Ceph based). I have one more Openstack cluster(Queens) which is completely separated from the Newton based one. I want to take the snapshot of VM's running in Newton based cluster and upload the snapshots in my Queens based cluster and create VM's out of them. But when I took snapshot of VM's which are booted from volume the snapshot size is showing 0bytes. How can I take snapshot of VM booted from volume so that I can upload it in other cluster??

openstack image show e6b67bd5-aa38-4951-89ec-1fc964f892af

+------------------+------------------------------------------------------------------------------------------------------------------------------------------------+
| Field            | Value                                                                                                                                          |
+------------------+------------------------------------------------------------------------------------------------------------------------------------------------+
| checksum         | d41d8cd98f00b204e9800998ecf8427e                                                                                                               |
| container_format | bare                                                                                                                                           |
| created_at       | 2018-10-08T08:23:18Z                                                                                                                           |
| disk_format      | qcow2                                                                                                                                          |
| file             | /v2/images/e6b67bd5-aa38-4951-89ec-1fc964f892af/file                                                                                           |
| id               | e6b67bd5-aa38-4951-89ec-1fc964f892af                                                                                                           |
| min_disk         | 0                                                                                                                                              |
| min_ram          | 0                                                                                                                                              |
| name             | TEST_Image_Master-2018-10-08-10-23                                                                                                         |
| owner            | d160f4259e2e464ea3f9fb0c7ea39571                                                                                                               |
| properties       | base_image_ref='', bdm_v2='True', block_device_mapping='[{"guest_format": null, "boot_index": 0, "delete_on_termination": false, "no_device":  |
|                  | null, "snapshot_id": "39cfe636-18b8-48aa-be3d-f0e48e135fb8", "device_name": "/dev/vda", "disk_bus": "virtio", "image_id": null, "source_type": |
|                  | "snapshot", "tag": null, "device_type": "disk", "volume_id": null, "destination_type": "volume", "volume_size": 40}]',                         |
|                  | root_device_name='/dev/vda'                                                                                                                    |
| protected        | False                                                                                                                                          |
| schema           | /v2/schemas/image                                                                                                                              |
| size             | 0                                                                                                                                              |
| status           | active                                                                                                                                         |
| tags             |                                                                                                                                                |
| updated_at       | 2018-10-08T08:23:19Z                                                                                                                           |
| virtual_size     | None                                                                                                                                           |
| visibility       | private                                                                                                                                        |
+------------------+------------------------------------------------------------------------------------------------------------------------------------------------+
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Can you share the output of openstack image show SNAPSHOT? As admin user, just in case.

Bernd Bausch gravatar imageBernd Bausch ( 2018-10-08 10:58:41 -0500 )edit

openstack image show SNAPSHOT is updated in the question

vathanlal gravatar imagevathanlal ( 2018-10-09 03:37:16 -0500 )edit
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answered 2018-10-09 07:14:59 -0500

eblock gravatar image

First I have to ask, are you aware of the recommendation to use raw images for Ceph? I wrote a small blog post to show the difference between raw and qcow2 images.

To answer your question about the size of 0 Bytes. If you create the instance snapshot via Horizon you'll probably end up with a qcow2 disk-format for the new image, at least that was set in my case. If you create the snapshot from the command line you can choose the disk-format. You can't change the disk-format after the snapshot has been uploaded.

For comparison I created two glance images from of a running VM (based on a volume):

control:~ #  imagelist.sh snap
+--------------------------------------+--------------------+-------------+------------------+---------+--------+
| ID                                   | Name               | Disk Format | Container Format | Size    | Status |
+--------------------------------------+--------------------+-------------+------------------+---------+--------+
| 391f5061-378b-4ebb-a1f5-8a347ee540b0 | test-vol-snap      | qcow2       | bare             | 0B      | active |
| 49b9755f-92aa-4c91-98a4-ebd67b3958cb | test-vol-snap2     | raw         | bare             | 1GB     | active |
+--------------------------------------+--------------------+-------------+------------------+---------+--------+

(The script "imagelist.sh" is a custom script I created to give some more information about the images)

As you can see, these two images also differ in size. test-vol-snap was created from Horizon resulting in a qcow image, snap2 was created via command line resulting in a raw image. You can create the image like this (CLI):

control:~ #  openstack image create --volume d7b75639-47ae-46d3-a72e-0795ac88a1c2 --disk-format raw test-vol-snap2
+---------------------+--------------------------------------+
| Property            | Value                                |
+---------------------+--------------------------------------+
| container_format    | bare                                 |
| disk_format         | raw                                  |
| display_description |                                      |
| id                  | d7b75639-47ae-46d3-a72e-0795ac88a1c2 |
| image_id            | 49b9755f-92aa-4c91-98a4-ebd67b3958cb |
| image_name          | test-vol-snap2                       |
| protected           | False                                |
| size                | 1                                    |
| status              | uploading                            |
| updated_at          | 2018-10-09T11:42:24.000000           |
| visibility          | shared                               |
| volume_type         | None                                 |
+---------------------+--------------------------------------+
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Asked: 2018-10-08 07:31:02 -0500

Seen: 128 times

Last updated: Oct 09 '18

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