Ceph: CT virtual drive in both storages <pool>_ct and <pool>_vm

[cmonty14]

Hello!
After creating a pool + storage via WebUI I have created a container.

The virtual disk of this container is defined as a block device image in Ceph:
root@ld4257:~# rbd ls pve
vm-100-disk-1

However when I check content of the available storages
pve_ct
pve_vm
I can see this image vm-100-disk-1 in both.

In my understanding this makes no sense because the storage pve_ct uses a specific attribute KRBD.

Question:
Why is the virtual disk displayed in both storages pve_ct and pve_vm?

 

[alexskysilk]

pve_ct and pve_vm are two pointers to the same pool; the distinction being using krbd for access for containers.

 

[cmonty14]

I'm sorry, but I don't get this.
The pool is obviously pve.
If pve_ct and pve_vm are pointers, then this is not a Ceph thing?

Checking the properties of storage pve_ct and pve_vm the difference is clear: pve_ct has KRBD enabled.

Does it mean PVE is creating an image with attribute KRBD for virtual disk when creating a CT and an image w/o any attribute when creating a virtual disk of a VM?

Displaying the same image in both storages pve_ct and pve_vm is very confusing, though.

 

[alexskysilk]

If pve_ct and pve_vm are pointers, then this is not a Ceph thing?

no, its a proxmox thing. this is the basis for proxmox storage model (https://pve.proxmox.com/pve-docs/chapter-pvesm.html)

Does it mean PVE is creating an image with attribute KRBD for virtual disk when creating a CT and an image w/o any attribute when creating a virtual disk of a VM?

As you've pointed out, the data itself resides on the same ceph pool; the mounting manner has no bearing on the data itself. When you set the krbd flag to a proxmox storage pool, you're instructing proxmox to use the krbd kernel driver to mount the disk.

 

[cmonty14]

OK.
The storage definition is clear.
root@ld4257:# cat /etc/pve/storage.cfg
dir: local
path /var/lib/vz
content vztmpl,backup,iso

rbd: pve_vm
content images
krbd 0
pool pve

rbd: pve_ct
content rootdir
krbd 1
pool pve

However imo it's inconsistent to display a virtual disk belonging to a CT in storage <poolname>_ct and vice versa.