Qcow2 disk and provisioning

[frankz]

Hello everyone, I have in nfs several disks in qcow2 in this format. I know that there is the possibility for the system to report to the user that the number of VMs with thin disks can exceed the altitude beyond which space problems can occur. over-provisioning

How to do it?

 

[fiona]

Hi,
you're probably thinking about LVM-thin which has such a feature (it's reported automatically by the LVM tools when allocating). For file-system based storages, that is not easily possible as, in principle, you need to scan all files and sum up the thin files (in Proxmox VE, we could check only the images we control, but nothing like this is implemented at the moment). There is a preallocation option you can set to falloc to avoid thin provisioning, but with NFS you might run into timeouts upon disk creation then.

 

[frankz]

Hi,
you're probably thinking about LVM-thin which has such a feature (it's reported automatically by the LVM tools when allocating). For file-system based storages, that is not easily possible as, in principle, you need to scan all files and sum up the thin files (in Proxmox VE, we could check only the images we control, but nothing like this is implemented at the moment). There is a preallocation option you can set to falloc to avoid thin provisioning, but with NFS you might run into timeouts upon disk creation then.

Yes, qcow2 is probably referred to lvm volumes. Thanks for the clarification.

So I ask you: how best to manage this allocation on nfs without incurring space problems?

 

[fiona]

So I ask you: how best to manage this allocation on nfs without incurring space problems?

As I suggested, you can try using preallocation=falloc. But if that causes timeouts, I'm afraid you'd have to wait for this enhancement to be implemented (unfortunately not high-priority and a bit of work, because it works differently for different storage types).