Being careful with physical disks

Being careful with physical disks

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One of the features of Hyper-V is that you can to connect a physical disk directly to a virtual machine.  You can only do so if the disk is "offline" in the parent partition, this is necessary to avoid the data corruption that could occur if two operating systems tried to write to the same disk at the same time.

Unfortunately it is still possible to get into this bad situation.  Two ways to do this are to:

  1. Start a virtual machine with a physical disk connected to it - and then go and online that disk in the parent partition.  This is not blocked today and will cause much mayhem (and potential data loss).
  2. Use tools that perform low level disk access in the parent partition.

I accidentally did the second one the other day when I was running some vendor specific disk test tools in the parent partition and had forgotten that I had the disks assigned to a running virtual machine.

In the future we would like to detect and block these scenarios - but for now it is up to the user to be careful when it comes to using physical disks in a virtual machines.


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  • Please add 3 and 7 and type the answer here:
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  • Seems like Hyer-v could do some interesting things in the future by mounting a Raid-5 volume in both the guest and host operating sytems without causing any harm.  What are your thoughts?

  • Is there a way - maybe manual editing of the description file - you could connect a physical disk to a virtual machine also when running Virtual PC 2007 ?


    Happy new year !

  • Scott Weeden -

    We have no plans for that at the moment.  This is something we would like to stop from happening.

    Czerno -

    No, you cannot do this with Virtual PC 2007.



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