started preclear on wrong device - help needed rescuing content

nastard · November 25, 2020

I am quite new to Unraid. My current setup contains 3x4TB & 2x8TB HDDs plus a 500GB Cache SSD and a 1TB NVME SSD.

One of the 4TB HDDs and the 1TB SSD were not part of the array yet.

The 1TB was passed through to a Windows VM. On it there is an NTFS partition (after an EFI partition and some 100MB spare space) holding two vhdx files, both holding a Windows installation and being bootable into from the Windows bootloader (screenshot only shows one of the VHDXes being mounted in Windows, the "virgin" one at the time being booted from):

The reason I did it like this and not, say, put the virtual disks in the domains share, is that I wanted to still be able to natively boot into these Windows systems. The 1TB SSD was precleared before using it for passthrough, so there shouldn't be any other data on it.

One of the VHDXes was a clone of my previous Windows installation I ran natively from the 500GB SSD. There is data on there that I didn't yet save elsewhere. The other was a relatively new Windows installation which would be no big deal if lost. I believe the fresh install was on the SSD first, so it might be in the front of the space if that's how it works.

What I wanted to do: start preclear for the last remaining 4TB HDD (that process is now running on the screenshot above).

What I did instead: started preclear (without pre-read of course, because who has time for that) on the 1TB SSD. While at the time even running Windows off of the virgin Windows VHDX on the 1TB SSD. While being with my mind elsewhere. That's not a good idea. Lesson learned. (Still, @gfjardim, if you read this, thanks for the preclear plugin but please disable preclearing start for certain "unassigned devices", like for instance those marked as "Pass Thru" or those currently passed through but not marked like that or even force users to format the device manually first and only start preclear if there is a single empty partition or so. And/or give the user a view of the partition table and let them confirm that they want to override these partitions. That would have saved me from my own stupidity). This is what I started:

So before I realized my mistake, and cancelled the process, the dd ran for like a few seconds.

Windows still ran for a bit but certain things stopped working and I had to "force stop" the VM. Afterwards, it wouldn't boot anymore.

This was the preclear log after I pressed the big red emergency button:

This is approximately what I assume happened, and a sketch of the device situation:

Of course, the first thing I did was create a backup of the drive with dd before testing my luck with testdisk.

But until now, I wasn't able to restore the partition with testdisk. The analysis finds some partitions, but none that have the label that I am expecting or where I am able to "list files". Again, I am looking for an NTFS partition with two huge VHDX files on it.

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