Disk speed always gets updated to same value if set to all zeros

[mater-345]

Hi,

Describe the bug
After setting the disk speed to 0 (unlimited), rerun always wants to set the same 0 value again for the VM.

To Reproduce
Steps to reproduce the behavior:

1. Create a resource

resource "proxmox_virtual_environment_vm" "vm-disk-speed-tester" {
  bios          = "seabios"
  vm_id         = "606"
  name          = "vm-disk-speed-tester"
  scsi_hardware = "virtio-scsi-pci"
  node_name     = "proxmox01"
  timeout_clone = 180
  timeout_create = 180
  timeout_migrate = 180
  timeout_reboot = 180
  timeout_shutdown_vm = 180
  timeout_start_vm = 180
  timeout_stop_vm = 180

  agent {
    enabled = "true"
    timeout = "3m"
  }
  cpu {
    cores   = 4
    sockets = 1
    type    = "qemu64"
  }

  disk {
    datastore_id = "ceph-ha"
    interface    = "scsi0"
    file_format  = "raw"
    size         = 52
    cache        = "writeback"
    discard      = "on"
    speed {
      iops_read            = 0
      iops_read_burstable  = 0
      iops_write           = 0
      iops_write_burstable = 0 
      read                 = 0
      read_burstable       = 0
      write                = 0
      write_burstable      = 0
    }
  }
...

2. Run terraform apply after the VM created:
3. Runterraform apply again:

proxmox_virtual_environment_vm.vm-disk-speed-tester: Refreshing state... [id=606]

Terraform used the selected providers to generate the following execution plan. Resource actions are indicated with the following symbols:
  ~ update in-place

Terraform will perform the following actions:

  # proxmox_virtual_environment_vm.vm-disk-speed-tester will be updated in-place
  ~ resource "proxmox_virtual_environment_vm" "vm-disk-speed-tester" {
        id                      = "606"
        name                    = "vm-disk-speed-tester"
        # (26 unchanged attributes hidden)

      ~ disk {
          ~ discard           = "ignore" -> "on"
          ~ iothread          = true -> false
            # (12 unchanged attributes hidden)

          + speed {
              + iops_read            = 0
              + iops_read_burstable  = 0
              + iops_write           = 0
              + iops_write_burstable = 0
              + read                 = 0
              + read_burstable       = 0
              + write                = 0
              + write_burstable      = 0
            }
        }

Expected behavior
Terraform should not try to change 0 value with a 0 value.

If the speed settings are on their default values, terraform doesn't want to change these values.

• Single or clustered Proxmox: Clustered Proxmox
• Proxmox version: 8.2.4
• Provider version (ideally it should be the latest version): latest 0.64.0
• Terraform/OpenTofu version: v1.9.5-1
• Debug logs (TF_LOG=DEBUG terraform apply):

[bpg]

Hi @mater-345! 👋🏼

If the speed block contains all zeros (i.e., its default value), it is treated as undefined. In other words, the provider can't distinguish between two configurations: one with a speed block set to all zeros, and another without a speed block. This means no remote configuration changes related to this block are applied to the remote VM, and nothing corresponding to this block is read back, making it inconsequential and thus removed from the state.

This behavior is not ideal, but it would be difficult to change in the current implementation. In #1231, we'll have more flexibility in managing the current state and defaults, so this use case could be handled differently in the future. However, for now, the provider can't properly support it.

I'm going to close it as "won't do" for 0.x, and we'll check this case in the future 1.x.