Why lvm volume with iscsi backend cannot take snapshot fonctionnality

[christophe.aron]

Hi,

I study the benefits of migrate ovirt virtualization platform to proxmox virtualization.
My infrastrucutre is based of 5 hypervisors and 1 SAN storage managed by ISCSI target.
On ovirt, I have multiple domain storage which use iscsi lun for disk storage and on my virtual machine I can manage snapshot,etc.
I setup a proxmox environment for POC and I have setup multipathing iscsi storage backend and mount LVM volume based in my iscsi target.
Then, I saw in virtual machine that is not possible to make snapshot because my backend storage doesn't support it.

I check this page :https://pve.proxmox.com/wiki/Storage:_iSCSI that confirm me I can't take snapshot on vm with this storage backand.
Why on Ovirt I can take snapshot and not in Proxmox?

 

[bbgeek17]

When using Proxmox, to be able to use Snapshots, you have to use LVM-Thin, but if you are using LVM thin you can't use this storage as shared (no allocation guarantees between multiple hosts).
In Ovirt, I suspect, they are using Qcow backing instead of LVM slices for disks. You can do it in Proxmox as well. Of course using Qcow on top of filesystem is not as efficient as using direct LVM slice.

This is why in our storage driver we implemented a creation of an iSCSI lun on-demand for each disk with automatic attachment. The snapshots are also offloaded to backend storage per lun.

I suspect you've seen this table, but in case you didnt, its very useful: https://pve.proxmox.com/wiki/Storage

 

[christophe.aron]

Hi,
It's work thank for your advice.
But, I think it must be a native feature in a virtual environment like Ovirt, HyperV, Vmware.

Best regards,