On Sat, Sep 25, 2021 at 7:37 AM Laurent Dumont <laurentfdumont@gmail.com> wrote:

Just to be sure, the flow is.
Create VM with root disk on a volume/image.
Create another 1TB volume.
Attach the volume to the VM as a second drive using a multi attach approach (https://docs.openstack.org/cinder/latest/admin/blockstorage-volume-multiattach.html)?
Create snapshot of the original VM (with it's root drive + 1 TB volume)?
Create new VM from snapshot.
Instead of a new VM + 1 new root volume + the same 1TB multiattach volume attached, you get a new multiattach volume (new volume ID and everything)?

Yes, here is the block device mapping of the snapshot (from a VM with 100GB of root disk and 1TB of multiattach volume)

block_device_mapping: [{"image_id": null, "delete_on_termination": true, "device_name": "/dev/vda", "disk_bus": "virtio", "volume_id": null, "volume_type": null, "destination_type": "volume", "source_type": "snapshot", "guest_format": null, "volume_size": 100, "device_type": "disk", "snapshot_id": "7b2c7f3a-8420-4a33-820e-2d2231d930c7", "boot_index": 0, "no_device": null, "tag": null}, {"image_id": null, "delete_on_termination": false, "device_name": "/dev/vdb", "disk_bus": null, "volume_id": null, "volume_type": null, "destination_type": "volume", "source_type": "snapshot", "guest_format": null, "volume_size": 1000, "device_type": null, "snapshot_id": "c2a0695f-8c9e-46f9-80a8-560c47521eeb", "boot_index": null, "no_device": null, "tag": null}]

openstack image list

+--------------------------------------+----------------+--------+

| ID | Name | Status |

+--------------------------------------+----------------+--------+

| e9e0e6dc-6389-49a3-bd52-467520cd2c9e | vm-04-snap-new | active |

+--------------------------------------+----------------+--------+

openstack volume list

+--------------------------------------+---------------+--------+------+--------------------------------------------------------------+

+--------------------------------------+---------------+--------+------+--------------------------------------------------------------+

Under volume >. snapshots

I can see two new volumes created

openstack volume snapshot list

+--------------------------------------+-----------------------------+-------------+-----------+------+

+--------------------------------------+-----------------------------+-------------+-----------+------+

+--------------------------------------+-----------------------------+-------------+-----------+------+

controller-1:~$ openstack server create --flavor WinGPU16 --image vm-04-snap-new --max 10 vm

+-------------------------------------+-------------------------------------------------------+

| Field | Value |

+-------------------------------------+-------------------------------------------------------+

| OS-DCF:diskConfig | MANUAL |

| OS-EXT-AZ:availability_zone | |

| OS-EXT-SRV-ATTR:host | None |

| OS-EXT-SRV-ATTR:hypervisor_hostname | None |

| OS-EXT-SRV-ATTR:instance_name | |

| OS-EXT-STS:power_state | NOSTATE |

| OS-EXT-STS:task_state | scheduling |

| OS-EXT-STS:vm_state | building |

| OS-SRV-USG:launched_at | None |

| OS-SRV-USG:terminated_at | None |

| accessIPv4 | |

| accessIPv6 | |

| addresses | |

| adminPass | se8pWoZ8AQ5Y |

| config_drive | |

| created | 2021-09-25T07:25:51Z |

| flavor | WinGPU16 (e3cd48c5-9675-42ad-a766-29b92c674224) |

| hostId | |

| id | facfc95d-bcb5-452c-a7fb-fcfa22f4257b |

| image | vm-04-snap-new (e9e0e6dc-6389-49a3-bd52-467520cd2c9e) |

| key_name | None |

| name | vm-1 |

| progress | 0 |

| project_id | 21639a96c609474390c837accd2de337 |

| properties | |

| security_groups | name='default' |

| status | BUILD |

| updated | 2021-09-25T07:25:51Z |

| user_id | 19faf07bb5da40b897e5dc73073cdec6 |

| volumes_attached | |

+-------------------------------------+-------------------------------------------------------+

controller-1:~$

controller-1:~$ openstack server list

+--------------------------------------+----------+---------+----------------------+----------------+----------+

+--------------------------------------+----------+---------+----------------------+----------------+----------+

+--------------------------------------+----------+---------+----------------------+----------------+----------+

controller-1:~$ openstack volume list

+--------------------------------------+---------------+--------+------+--------------------------------------------------------------+

+--------------------------------------+---------------+--------+------+--------------------------------------------------------------+

+--------------------------------------+---------------+--------+------+--------------------------------------------------------------+

As you can see the original multi attach volume "shared-volume" is attached to VM-03 but all the other 1TB volumes are not shared but directly attach only per one sevrer/vm.

Seems we have to attach the shared volume separately into each VM.

I've never had the pleasure to play around with this, but creating a new VM from a snapshot could mean a new volume too. I'm not sure how snapshot will work with multi volume VMs.

On Fri, Sep 24, 2021 at 11:20 AM open infra <openinfradn@gmail.com> wrote:
Hi,

I am planning to spin hundreds of servers with a shared storage.
I have created one instance and attached a 1 TB volume (multiattach) and created a snapshot of the instance.
But when I spin another server using the snapshot, I noticed that instead of expected shared volume, individual 1 TB size additional (dedicated) volume has been attached to each VM.

Is there a mechanism where I can create multiple instances along with a shared volume attached to the instance instead of attaching later?

Regards,
Danishka