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Interesting feedbacks :)
It looks like the 'get-me-a-network' issue [1]. It's a detail implementation, choose for technical/business reasons, which broke the tests and the compatibility.
We will probably have other subject like this one.

Do we already speak about providing different level for each program? I'm not speaking about guidelines which target the releases. I'm speaking about:
- OpenStack Powered compute containing
- OpenStack Powered compute basics (get-me-a-network, get-me-a-compute, get-me-a-storage)
- OpenStack Powered compute advanced (boot-from-volume, boot-from-image, resize-a-instance, get-a-floating-ip, ...)

Maybe we should add another level between basics and advanced.

[1] http://specs.openstack.org/openstack/neutron-specs/specs/liberty/get-me-a-network.html

--
Jean-Daniel Bonnetot
http://www.ovh.com
@pilgrimstack




Le 2 sept. 2016 à 08:47, Zhenyu Zheng <zhengzhenyulixi at gmail.com<mailto:zhengzhenyulixi at gmail.com>> a écrit :

Hi All,

We are deploying Public Cloud platform based on OpensStack in EU, we are now working on DefCore certificate for our public cloud platform and we meet some problems;

OpenStack(Nova) supports both "boot from Image" and "boot from Volume" when launching instances; When we talk about large scale commercial deployments such as Public Cloud, the reliability of the service is been considered as the key factor;

When we use "boot from Image" we can have two kinds of deployments: 1. Nova-compute with no shared storage backend; 2. Nova-compute with shared storage backend. As for case 1, the system disk created from the image will be created on the local disk of the host that nova-compute is on, and the reliability of the userdata is considered low and it will be very hard to manage this large amount of disks from different hosts all over the deployment, thus it can be considered not commercially ready for large scale deployments. As for case 2, the problem of reliability and manage can be solved, but new problems are introduced - the resource usage and capacity amounts tracking being incorrect, this has been an known issue[1] in Nova for a long time and the Nova team is trying to solve the problem by introducing a new "resource provider" architecture [2], this new architecture will need few releases to be fully functional, thus case 2 is also considered to be not commercially ready.

For the reasons I listed above, we have chosen to use "boot from Volume" to be the only way of booting instance in our Public Cloud, by doing this, we can overcome the above mentioned cons and get other benefits such as:

Resiliency - Cloud Block Storage is a persistent volume, users can retain it after the server is deleted. Users can then use the volume to create a new server.
Flexibility - User can have control over the size and type (SSD or SATA) of volume that used to boot the server. This control enables users to fine-tune the storage to the needs of your operating system or application.
Improvements in managing and recovering from server outages
Unified volume management

Only support "boot from Volume" brings us problems when pursuing the DefCore certificate:

we have tests that trying to get instance list filtered by "image_id" which is None for volume booted instances:

tempest.api.compute.servers.test_create_server.ServersTestJSON.test_verify_server_details
tempest.api.compute.servers.test_create_server.ServersTestManualDisk.test_verify_server_details
tempest.api.compute.servers.test_list_server_filters.ListServerFiltersTestJSON.test_list_servers_detailed_filter_by_image
tempest.api.compute.servers.test_list_server_filters.ListServerFiltersTestJSON.test_list_servers_filter_by_image

    - The detailed information for instances booted from volumes does not contain informations about image_id, thus the test cases filter instance by image id cannot pass.


we also have tests like this:

tempest.api.compute.images.test_images.ImagesTestJSON.test_delete_saving_image

    - This test tests creating an image for an instance, and delete the created instance snapshot during the image status of “saving”. As for instances booted from images, the snapshot status flow will be: queued->saving->active. But for instances booted from volumes, the action of instance snapshotting is actually an volume snapshot action done by cinder, the image saved in glance will only have the link to the created cinder volume snapshot, and the image status will be directly change to “active”, as the logic in this test will wait for the image status in glance change to “saving”, so it cannot pass for volume booted instances.


Also:

test_attach_volume.AttachVolumeTestJSON.test_list_get_volume_attachments

    - This test attaches one volume to an instance and then counts the number of attachments for that instance, the expected count was hardcoded to be 1. As for volume booted instances, the system disk is already an attachment, so the actual count of attachment will be 2, and the test fails.

And finally:

tempest.api.compute.servers.test_server_actions.ServerActionsTestJSON.test_rebuild_server
 tempest.api.compute.servers.test_servers_negative.ServersNegativeTestJSON.test_rebuild_deleted_server
tempest.api.compute.servers.test_servers_negative.ServersNegativeTestJSON.test_rebuild_non_existent_server

    - Rebuilding action is not supported when the instance is created via volume.


All those tests mentioned above are not friendly to "boot from Volume" instances, we hope we can have some workarounds about the above mentioned tests, as the problem that is having with "boot from Image" is really stopping us using it and it will also be good for DefCore if we can figure out how to deal with this two types of instance creation.


References:
[1] Bugs related to resource usage reporting and calculation:

* Hypervisor summary shows incorrect total storage (Ceph)
  https://bugs.launchpad.net/nova/+bug/1387812
* rbd backend reports wrong 'local_gb_used' for compute node
  https://bugs.launchpad.net/nova/+bug/1493760
* nova hypervisor-stats shows wrong disk usage with shared storage
  https://bugs.launchpad.net/nova/+bug/1414432
* report disk consumption incorrect in nova-compute
  https://bugs.launchpad.net/nova/+bug/1315988
* VMWare: available disk spaces(hypervisor-list) only based on a single
  datastore instead of all available datastores from cluster
  https://bugs.launchpad.net/nova/+bug/1347039

[2] BP about solving resource usage reporting and calculation with a generic resource pool (resource provider):

https://git.openstack.org/cgit/openstack/nova-specs/tree/specs/newton/approved/generic-resource-pools.rst


Thanks,

Kevin Zheng
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