Windows Server 2012 R2 new install in Azure, with an odd behaviour: when loading an ISO file (right click in Explorer, select Mount), instead of mounting on the existing CD drive E:, it creates a new CD drive, on the first available letter, G:, and mounts it there. When I eject G:, it unmount the ISO and the drive just disappears from the list.

No other software installed, it's the stock February 2015 Azure image.

Looked at doing it via Powershell, but Mount-DiskImage doesn't have a parameter for the target drive or letter.

Any way to fix this ?

  • I would expect it to work as you describe. Why do you call this odd behaviour? Any disc mounting software that I have encountered mounts to an unassigned drive letter. – AFH Mar 26 '15 at 16:52
  • After mounting you should be able to use diskpart to reassign the drive letters. – AFH Mar 26 '15 at 16:56
  • You are right. Thank you ! :) drive E: seems designed for the Azure backend and there's no way to mount something else there. Changing the drive letters would most likely mess up the system, as the install source files won't be available anymore, in case I need to install extra features. Will just change all my scripts to use the next available letter. – Razvan Zoitanu Mar 26 '15 at 17:22

The best way for me to solve this is mount without a drive letter, and assign a letter (less likely to be used by some Azure internal process, like V) with a second command.

Mount-DiskImage -ImagePath "C:\ISO\My.iso" -NoDriveLetter
Get-Partition -DiskNumber 3 | Set-Partition -NewDriveLetter V

As mentioned in my comment and the link below, this is the expected behaviour, the E: drive is used by Azure in the marketplace images. If you'd like to read more about why I've been looking at this problem: https://www.codeisahighway.com/prepare-data-disks-for-stability-and-consistency-in-azure-throughout-virtual-machines-and-scale-sets-lifecycle/

it was a CD-ROM drive used by Microsoft that was causing this behavior. When dealing with some Azure marketplace images (Generalized), Microsoft will use this drive as a bootstrap point to properly license Windows & configure the OS. When the virtual machine agent enter a ready state and everything is fine, this drive is no longer needed and will be purged eventually, therefore vanishing at some point in the lifecycle of the virtual machine. [...] In my scenario, I was creating a virtual machine scale sets and was starting to assign my first data disk drive letter as F. I used an initialization script I took from the Azure documentation. It worked very well until I needed to re-image instances or perform an OS upgrade in the scale sets. When I did this, the instances were back running but with my data disk with letter E instead of F. It goes without saying that this made my application crash because it was referring to a data location of F:... in its configuration.

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