LVM shared FC storage - snapshot as a chain - status of storage API

[rbremer]

Using VE 9.2.3 in a distributed FC shared storage environment (LVM shared LUN with snapshot as a chain set to 1), taking snapshots of a VM (manually or via PBS) works fine. However, the API to perform a volume copy (task a snapshot of an individual disc) seems to be either not implemented at all or doesn't execute the necessary steps. I am fully aware this is an experimental API.

Steps to reproduce:

1. pvesh create /nodes/node1/storage/Test/content --vmid 9999 --filename vm-9999-manualtest.qcow2 --size 1G
2. pvesm list Test -> `Test:vm-9999-manualtest.qcow2 qcow2 images 1073741824 9999`
3. qemu-img info /dev/Test/vm-9999-manualtest.qcow2 --backing-chain:
   `
   image: /dev/Test/vm-9999-manualtest.qcow2
   file format: qcow2
   virtual size: 1 GiB (1073741824 bytes)
   disk size: 0 B
   cluster_size: 65536
   Format specific information:
   compat: 1.1
   compression type: zlib
   lazy refcounts: false
   refcount bits: 16
   corrupt: false
   extended l2: false
   Child node '/file':
   filename: /dev/Test/vm-9999-manualtest.qcow2
   protocol type: host_device
   file length: 1 GiB (1077936128 bytes)
   disk size: 0 B
   `
4. pvesh create /nodes/node1/storage/Test/content/vm-9999-manualtest.qcow2 --target vm-9999-snap-manualtest.qcow2
5. observe a task to be created and executed without errors.
6. pvesm list Test -> doesn't show the new target volume, same for qemu-img info or lvscan. it simply didn't get created.

The task log only shows this:
```
DEBUG: starting worker UPID:node1:001D91CC:0FF57329:6A54C460:imgcopy::root@pam:
DEBUG: end worker UPID:node1:001D91CC:0FF57329:6A54C460:imgcopy::root@pam:
TASK OK
```
and it takes no time at all.

So my question is, what is the status of the "copy volume" API, even though its still experimental, should it actually do something at the moment or is it a stub?

Thank you.

 

[bbgeek17]

Hi @rbremer ,

(manually or via PBS)

PBS does not take storage snapshots, perhaps you meant to use a different abbreviation here? Just clarifying this for the whole picture.

However, the API to perform a volume copy

Well, this API call is specifically marked as "do not use":
"https://pve.proxmox.com/pve-docs/api-viewer/#/nodes/{node}/storage/{storage}/content/{volume}"
You can look at the code here: https://github.com/proxmox/pve-storage/blob/master/src/PVE/API2/Storage/Content.pm#L545C1-L629C3

---

Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox

 

[rbremer]

Thank you for your reply. Indeed, that looks a lot like a stub to me. So I guess I have to wait before I can use K8S persistent volumes on the LVM storage ... Without snapshot based backups it ain't even an option. Hopefully Proxmox is working on getting those snapshots out of TP.

And yes, PBS doesn't do storage snapshots, I just confirmed that. Manually taking a snapshot works though.