Last week, I made a online backup of a virtual machine on Virtual Server 2005 R2 SP1 using the Advanced Open File Option of Symantec Backup Exec. Although, this is a questionable way to backup a virtual machine, I was curious if I could do the same with virtual machine under VMware Server.

The answer is yes, it works exactly the same. Backup and restore run through without any error messages. The restored virtual Windows server booted up without any complaints. However, when I logged on, I got the same message as under Virtual Server 2005 R2, i.e. that the system was shutdown unexpectedly.

This was no surprise. The question now is, if this is a recommendable way to back up virtual machines. In general, I would say no. However, there might be situations where this makes sense.

I discussed it already some days ago; the problem with this kind of backup is that you don’t get a consistent copy of the virtual machine. More or less, it is the same as if you just pulled the power plug on your server without shutting it down properly before.

In former times, this was the worst cardinal sin a Windows system administrator could ever commit. But Windows Server 2003 is much more robust than Windows NT. So, in most cases your Windows server will grant absolution if you repent sincerely. This is also true for many Windows server applications nowadays.

Therefore, backing up virtual machine files on a host system using the open file feature of your backup software might be an option. I used Backup Exec, but it probably works with any other professional backup solution as well. All you have to do is to check if all applications on the Windows server are robust enough to survive a hard reset of your server.

To be sure, I highly recommend making a second backup of your virtual servers using the conventional method, i.e. with a backup agent running on the guest system. This way, disaster recovery of all your virtual machines will be very fast using the backup you made of the virtual machine files. Then, if necessary, you can use the conventional backup of the guest system to restore the problematic virtual servers properly.

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