Migration from vmware 7.03 to proxmox-a pve-manager/9.0.10 - qemu-img: output file is smaller than input file

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on82

New Member
Jan 16, 2026
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Hi all

When importing machines using the GUI, all 100GB machines migrate without a problem, but if I have a machine with one 120GB drive and one 200GB drive, I get this message. Is this because my local drive is 343GB? My entire storage where I store the machines is 180TB. Or is this caused by something else?

What can I do to migrate such large machines?

Does anyone know what the problem might be?

create full clone of drive (ESX1:ha-datacenter/NAS/MyVM/MyVM.vmdk)
transferred 0.0 B of 1.0 KiB (0.00%)
qemu-img: output file is smaller than input file
Removing image: 100% complete...done.
TASK ERROR: unable to create VM 158 - cannot import from 'ESX1:ha-datacenter/NAS/MyVM/MyVM.vmdk' - copy failed: command '/usr/bin/qemu-img convert -p -n -f vmdk -O raw /run/pve/import/esxi/ESX1/mnt/ha-datacenter/NAS/MyVM/MyVM.vmdk 'zeroinit:rbd:vms.nvme/vm-158-disk-0:conf=/etc/pve/ceph.conf:id=admin:keyring=/etc/pve/priv/ceph/vms.nvme.keyring'' failed: exit code 1
 
It is likely because that qemu-img is misinterpreting the input VMDK size as only 1KiB (likely because the VMDK descriptor uses an incompatible version). This leads to the "output file is smaller than input file" failure, as the tool thinks it's dealing with a tiny file rather than your actual 120GB or 200GB disk.
 
on82 said:
Hi all

When importing machines using the GUI, all 100GB machines migrate without a problem, but if I have a machine with one 120GB drive and one 200GB drive, I get this message. Is this because my local drive is 343GB? My entire storage where I store the machines is 180TB. Or is this caused by something else?

What can I do to migrate such large machines?

Does anyone know what the problem might be?

create full clone of drive (ESX1:ha-datacenter/NAS/MyVM/MyVM.vmdk)
transferred 0.0 B of 1.0 KiB (0.00%)
qemu-img: output file is smaller than input file
Removing image: 100% complete...done.
TASK ERROR: unable to create VM 158 - cannot import from 'ESX1:ha-datacenter/NAS/MyVM/MyVM.vmdk' - copy failed: command '/usr/bin/qemu-img convert -p -n -f vmdk -O raw /run/pve/import/esxi/ESX1/mnt/ha-datacenter/NAS/MyVM/MyVM.vmdk 'zeroinit:rbd:vms.nvme/vm-158-disk-0:conf=/etc/pve/ceph.conf:id=admin:keyring=/etc/pve/priv/ceph/vms.nvme.keyring'' failed: exit code 1 omegle web
Click to expand...

Migrating VMs from VMware to Proxmox, the “output file is smaller than input file” error usually happens when qemu-img tries to write to storage that doesn’t support sparse files or thin provisioning properly or when the target storage format or RBD pool doesn’t have enough contiguous space.

A few things that helped me:
  1. Use the -S 0 option with qemu-img convert to disable sparse file handling.
  2. Make sure your target RBD or storage pool has enough free space for the full virtual disk size, not just used space.
  3. If possible convert to qcow2 first locally, then upload to Proxmox. it often avoids these errors with large disks.

This usually resolves migration issues for VMs with multiple large drives.
 
Last edited:
Hi @PinacaGina,
the first post shows that the detected size of the image is only 1KiB so it's unlikely to be related to sparse files or thin provisioning
 
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