Short version:

I want to copy a thin provisioned VMFS .vmdk from the free ESXI to a NAS for backup. How I do it? Are there any way which works out of the box? Naive copying doesn't work because it copies full size instead of actually provisioned size.

Note that the particular .vmdk format relies on VMFS sparse files. However there are other thin allocated image formats, including .vmdk used by Workstation, and .ovf. So exporting the images to those formats would work just fine.

Long versions:

I have a lab ESXi 6.0 server (I mean for experiments, not production) with a couple of VMs there. And I want to copy .vmdk files from the ESXI to my QNAP NAS for backup purposes.

However I don't want a full backup solution. I just want to keep the QNAP offline and backup like twice a year. At this pace the backup solutions, especially free solutions, don't survive well - they tend to rot due to dropping OS support, changing formats, forgetting passwords and so on.

So I want something with close to zero setup and maintenance. Recovery performance isn't important.

I have an up to 400 GB thin volume with 40 GBs actually used.

However a simple .vmdk download from the web-based Datastore Browser downloads full 400 GBs which doesn't look right to me.

The same goes with scp/sftp.

The only solution I have found so far is to lzop the image before downloading.

So the question is, are there any better ways which aren't overly complicated? For example Veeam requires remembering account password, using "corporate" email and downloading some 4GBs of their backup solution.

3 Answers 3


You can export sparse vmdk as “ordinary” vmdk with starwind v2v and save it on NAS - www.starwindsoftware.com/starwind-v2v-converter

The VM should be off during the export.


I have the best solution i think it works well in your scenario but bit out of the box bear with me.

Just create NAS Path

In esxi add new storage select NAS path and create a datastore

clone the VM's you want to backup and move those cloned VM's to NAS datastore that you've created and disconnect the NAS datastore.

you've a readily available backups that need to be mapped and powered on they only consume the used thin storage.

Hope it helps

  • This might work for me, but do you mean an NFS or iSCSI NAS path? iSCSI has a disadvantage that it's going to be another VMFS volume, which is hard to recover in case of partial disk failures. With NFS it might work if it creates a non-VMFS datastore (I'm not sure), but then it's 2 datastores and there are wide range of tools available such as free XSIBackup, which is sort of a more advanced version of vmdk tools.
    – nponeccop
    Feb 20, 2020 at 19:06
  • 1
    NFS path only which will be somewhat easy and Quick Feb 21, 2020 at 20:20
  • 1
    This would need another datastore setting up but as you need close to zero setup and maintenance this solution would cover all those and it pretty easy to recover also Feb 21, 2020 at 20:23
  • I would recommend encrypting vmdks of the vms though Feb 21, 2020 at 20:25

When you say "there are other thin allocated image formats, including .... .ovf".

What about OVF? If you're just talking about ad-hoc copies once or twice a year, not an automated backup solution, just right click your VM and Export (or for older versions File > Export > Export OVF Template).

It's main intended use is for redeploying prepared images to a new ESXi/vcenter, but it's basically just a copy of the machine so there's no reason you can't use it as a backup. If you want to be thorough you can test it by re-importing the exported copy to a new VM.

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