Migrate VM Backup from 3.0 to 1.8 / How to convert vma file to raw?

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Since release 2.3 Proxmox VE is using Virtual Machine Archive format (VMA)

How is it possible to backup a VM from a Proxmox VE 3.0 and restore it on a Proxmox VE 1.8?
Is there a converter to convert vma to raw/tar format?

Maybe there is only a special way to do the backup? We used
vzdump <id> -mode snapshot -dumpdir <targetdir>
and get a *.vma File.

If we use this file we will get this error:
pve:/backup# qmrestore vzdump-qemu-116-2013_07_25-12_51_47.vma 116
tar: This does not look like a tar archive
tar: Skipping to next header
tar: Error exit delayed from previous errors
ERROR: archive contaions no data

Thanks in advance for your help!

P.S:
we plan to update the pve 1.8 to 3.0, but it would be great if there would be a way to restore without updating the pve to 3.0.

 

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Re: Migrate VM Backup from 3.0 to 1.8 / How to convert vma file to raw? - solved

Maybe this is not the "official" way, but we just copied the /var/lib/vz/images/116/*.raw File to an empty VM on the 1.8 system.
It seems to work!

Steps
1.) Stop VM on source PVE
2.) create an empty VM on the destination PVE
3.) delete raw file of the new created VM on the destination PVE
4.) copy raw File from the source PVE to destination PVE /var/lib/vz/images/xxx/
5.) Start VM on destination PVE

Via vzdump we could not find a solution, it would be great to provide a vma converter (vma -> vmdk, raw...)