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Can I use a backup disk from one VM in another VM?

My colleagues and I have had several problems concerning VM backups because the files are open, and for other reasons. Our tentative plans to do backups always fail in the restore, including with backup software that is supposed to back up open files. We need a no-errors solution to this problem—it's an unacceptable situation to do a VM backup and later discover that you lost your files/VM.

If I backup a virtual disk with standard backup software, will it be possible to use this disk in another VM, without any problems? How?

Also, how do I backup/copy an entire VM without any risks?

Are there any auxiliary files that we must delete before a standard backup?

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Yes, if you backup a virtual disk with standard backup software, you can use the disk in another VM. To eliminate the file-in-use (open) issues, you need to utilize the snapshot features integrated in the VMware product. This will do three things to allow for a clean and successful backup:
  1. It will tell the virtual machine to dump cache so that all of the disk and memory of the running VM is committed.
  2. It creates a set of delta files where any new writes with the VM is performed.
  3. It frees up the virtual disk so that the files can be copied or backed up.

Once this is completed, you can copy the raw virtual machine disk's memory and configuration files to another machine and back them up from there.

After the VM files have been copied, you will then commit the delta back into the virtual machine.

No files need to be deleted if the above steps are followed.

This was first published in April 2007

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