Windows Server 2012 Cannot Read Disk As Guest OS In ESXI

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A server stack is the collection of software that forms the operational infrastructure on a given machine. In a computing context, a stack is an ordered pile. A server stack is one type of solution stack — an ordered selection of software that makes it possible to complete a particular task. Like in this post about Windows Server 2012 Cannot Read Disk As Guest OS In ESXI was one problem in server stack that need for a solution. Below are some tips in manage your windows server when you find problem about windows, vmware-esxi, virtual-machines, , .

I’m running into a frustrating issue with Windows Server 2012 and VMWare ESXI.

I’m running ESXI version 6.5 (old I know, but this is not the issue) with a VM running Windows Server 2012. On this VM, I had a second disk (named windows2012-1.vmdk) attached as drive A: without any issue. I wanted to reinstall Windows Server 2012, so I powered off the VM, removed the windows2012-1.vmdk HDD via Actions -> Edit Settings -> and clicked the “x” next to the drive. I left the “Delete files from datastore” box unchecked. I then reinstalled Windows Server 2012 on the 40GB drive as a fresh install, not an upgrade. After this was done, I went back into Edit Settings to re-add the windows2012-1.vmdk file and it appeared to be added just fine via ESXI, however the disk is not showing up in the OS.

Disk Management does not show any disk other than the 40GB OS disk, and a rescan does not show the new drive. The drive does, however, show up in Device Manager as “VMware Virtual disk SCSI Disk Device” same as the 40GB one. Uninstalling/Reinstalling the driver does not work, nor does updating the driver. The windows2012-1.vmdk also appears to be recognized in the BIOS as well (although it doesn’t have an OS on it so I can’t boot from it).

Limitations, the windows2012-1.vmdk file is 5TB and I do not have any external HDDs to export it to for another month. I have the important files backed up (about 1TB of the 5TB) but do not have a backup of the other ~3.5TB.

Any thoughts as to why this might happen?

You can try attching the VMDK to other VM (maybe Windows Server 2019 or any Linux VM) and try mounting VMDK inside. Alternatively there are various options to get contents of the VMDK. Might help:

I would never use the UI to perform this kind of task. The UI is an abstraction layer and any wrong assumption, caused by some little misunderstanding or some functional change/improvement in the UI, can lead to data loss.

The kind of operation that you are describing should be performed from the ESXi shell. That way you do see the files at play and you have direct control on the config files.

All virtual disks are attached to the VM at the .vmx file. You can edit it with vi and see all disks there. This little command will show you the lines in the .vmx file corresponding to the .vmdk disks.

cat /path/to/VM.vmx | grep ".vmdk"

You may easily swap, add or remove virtual disks from the .vmx file with the guarantee that anything edited there is straight and no asumptions or knowledge on the UI functioning is required. I like to say that primary actions should always be performed with primary tools, that way you remove uncertainties.

(*) Just don’t forget that on addition to the -flat.vmdk file name and depending on what you are doing, you might need to edit the .vmdk descriptor file (a text file), that points to the corresponding -flat.vmdk file. If you are just swapping disks you can abstract from that.

That said:

A .vmdk disk containing a working NTFS file system should be recognized by the Windows server guest. What you are describing seemingly points at some issue around the FS in the -flat.vmdk disk.

In regards to moving data off the host. We provide free ESXi backup & replication tools that will work even in the unlicensed ESXi version.

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