If IDE was used during the initial VM setup and needs to be changed to VirtIO later, this can be done through the Proxmox GUI without reinstalling the OS. The VM will need to be powered off first, and then the virtual disk needs to be removed through the Proxmox GUI. After clicking on Remove, the virtual disk will become unused, as shown in the following screenshot:
Double-click on the unused virtual disk or navigate to Add | Hard Disk to add it back to the VM. Select VirtIO as Bus/Device from the dialog box. It is very important ...
