I use two-way mirror feature of Windows 8 to regularly and transparently backup my important disks on USB drive.

Size of my USB drive is much higher than size of disk to backup, so allocating whole USB drive does not make any sense.

So I decided to use Virtual Hard Disk with needed size located on USB drive.

I mounted and added that vhdx to my mirror and everything works well until I need to disconnect my USB.

I cannot unplug my USB nicely (Eject) because it gives me disk still in use message. I cannot detach my vhdx in diskpart with some other error message. But I can put my whole USB drive offline in "Disk Management" and then Eject works.

So I work on my degraded storage space, speed is good (better than with second half connected).

Then I connect my USB drive with second half on it and put it online in "Disk Management".

The second half does not immediately appear in Storage space.

I open my USB drive in Windows Explorer, right click on my vhdx file and click Mount.

I get error message with window title "Couldn't mount file" and body starting with "The disk image isn't initialized".

I click Ok button.

Then I look at my Storage Spaces and see that second half of my mirror happily appeared and Storage Space is in "Repairing" cycle.

Then "Repairing" cycle finishes successfully and my Storage pool is green = happy.

Everything works like I wanted and I am happy, but not green :) because of that 1 thing - that nasty error message.

How can I mount my VHDX to avoid that error message and have it appear in my Storage pool at the same time ?

Does that error message indicate that I will have some problem in the future ?


By offlining the USB drive in disk management, you're essentially "pulling the plug" on the VHDX disk. This can cause corruption on the disk due to any writes that were in-progress at the time. If the disk reports as uninitialized, it may be due to damage to the partition table or file system MFT. If you're relying on this method for your primary or sole backup solution... I would highly recommend another option. Find some free backup software that uses a VSS snapshot of the disk to perform a file-based backup, or find a way to clone your disk from some bootable media while windows isn't running... Otherwise you may find yourself struggling to repair the VHDX when you truly need it.

  • Is it possible to unmount that VHDX nicely ? – alpav Mar 3 '15 at 14:45
  • How are you performing the mirror? It may not be possible without offlining the entire mirror, else you'd just have to shut the system down. – JimNim Mar 4 '15 at 0:11

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