How disks works on Proxmox?

[jolle]

Hi I am working with proxmox for about a month and I have learned a lot of things about virtualization and backups.
One thing that I have not understand exactly is what is happening to the disks. For example:
Lets say that we have 2 Nodes ( VM-server, VM-backup). On every node we have 3 physical disks ( disk1,disk2.disk3).
So if I go to the Datacenter->Storage and create a LVM with name disk1 and set it for both nodes to see it. What is actually happens to the nodes??
is it the same if I use ZFS ??
Also when I go to storage when I create a disk there what is going on to the system??

Thank you for your time!

 

[aaron]

and set it for both nodes to see it.

Not much. LVM is not a shared storage. See https://pve.proxmox.com/pve-docs/pve-admin-guide.html#_storage_types

Also when I go to storage when I create a disk there what is going on to the system??

It depends on the storage type. On LVM a new logical volume is created that is then handed over to the VM as block device. On ZFS a new ZVOL is created which can be used as block device.
This is similar for Ceph RBD.

On a directory storage, a file is created. Either a .raw or .qcow(2) that stores the disk and is handed over to the VM as a block device.

Containers are a bit special. On LVM or a directory storage, by default, they also get block devices which are ext4 formatted. On ZFS they get a subvolume which is a regular file system that can be accessed easily from the host.

So, in short, depending on the storage type it comes down to having something that can be used as a block device in the VM so the VM can partition and format it's virtual disk.