Migrating VMs from Unraid to Proxmox — a practical checklist

Migrating a VM from Proxmox to Unraid does not end with just copying the disk image. If even one of the firmware, TPM, disk controller, or network model is mismatched, it will stop at the boot stage. This is the procedure I organized while reviewing 7 actual machines.

1. Preliminary assessment — first determine whether the VM can be moved

The first thing to check is whether BitLocker and TPM are in use. If TPM 2.0-based BitLocker is enabled on Windows 11 series, migration without securing the decryption key leads to data loss.

• Check BitLocker status: manage-bde -status
• Back up recovery keys (export to AD or a file)
• Separately store the Proxmox-side TPM state image (qm config)
• If there are snapshots, delete them before migration — disks with snapshots are excluded from conversion targets

2. Disk conversion — from LVM-thin to qcow2

Proxmox's default storage is LVM-thin. Unraid is qcow2 file-based, so format conversion is required. The principle is to work on a copy without touching the original.

# On the Proxmox host (VM stopped)
qemu-img convert -p -O qcow2 \
  /dev/pve/vm-105-disk-0 \
  /mnt/backup/vm-105-disk-0.qcow2

# After copying to the Unraid domains share
qemu-img info vm-105-disk-0.qcow2   # check virtual size

After conversion, be sure to check that the virtual size matches the original provisioning size. Since qcow2 is sparse, it is normal for the file size (df) and virtual size to differ.

3. Machine types and firmware

If you change a VM installed with SeaBIOS to q35 + OVMF, it will not boot. The safest approach is to match the original machine type exactly. If you must use OVMF (e.g., TPM 2.0, Secure Boot), you need to prepare a separate EFI partition.

4. Cache placement — where performance diverges

Unraid's array is slow for writes due to parity computation. It is recommended to always place VM disks on the cache pool (NVMe) and configure the cache as a mirror.

If the cache is a single NVMe, that one disk becomes a SPOF for all VMs. The system I was actually reviewing also had a non-mirrored cache, so I raised it as an improvement item.

5. Post-migration checks

• Whether the network MAC changes → recheck the guest internal settings for VMs using static IPs
• Whether time synchronization (NTP) is working properly
• Presence of VirtIO drivers (Windows requires the virtio-win ISO)
• Verify that the backup job points to the new path