flat *.vmdk file needs full diskspace after uploading form datastore

I have a VM with a flat vmdk File ("Filename.vmdk" / Full HD space 40 GB / used space in datastore 23 GB) on my ESX Host (Version 5.5)
For a backup of the full VM I uploaded the full folder from the datastore to my backup server (Windows Server 2012). I used vSphere Client 5.5.

On the Backupserver I finde the VMDK two vmdk files:
- Filename.vmdk with 1KB
- Filename-flat.vmdk wiht 41 GB !!!

Why did my flat VMDK File grow to the full space by uploading form the datastore? What can I do to not have this effect?

Thanks for your help.
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Andrew Hancock (VMware vExpert / EE MVE^2)Connect With a Mentor VMware and Virtualization ConsultantCommented:
Possibly because the VMDK format is a Thinly provisioned.

This is to be expected that the Thin disk will inflate when copied to a non VMFS (VMware) datastore.

Have you tried:-

Part 10: HOW TO: Backup (Export) and Restore (Import) virtual machines to VMware vSphere Hypervisor 5.1 for FREE

because exporting only exports the used data, in the VMDK, but maintains the file VMDK format, you may find this a better way or storing files, using less storage space.
ICSAutomationAuthor Commented:
Perfect! Thanks for explaning!! :-)
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