A disk shows on attached on VM. but Couldn't see it on VM.

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A disk shows on attached on VM. but Couldn't see it on VM.

shijin zen 40

A disk shows on attached . but Couldn't see it on VM. User's image

TP 131.7K Reputation points Volunteer Moderator

2025-08-06T17:56:31.04+00:00

Hi,

Inside of the VM, are you able to see it, create partition, format, assign drive letter, etc? For example, for Windows VM you could connect to the VM using RDP, right-click on Start button and choose Disk Management. You should see the disk and be able to partition/format/assign drive letter to it.

-TP
shijin zen 40 Reputation points

2025-08-07T16:16:31.5266667+00:00

No, I couldn't see anything inside of the VM about the disk.

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TP 131.7K Reputation points Volunteer Moderator

2025-08-06T17:56:31.04+00:00

Hi,

Inside of the VM, are you able to see it, create partition, format, assign drive letter, etc? For example, for Windows VM you could connect to the VM using RDP, right-click on Start button and choose Disk Management. You should see the disk and be able to partition/format/assign drive letter to it.

-TP
shijin zen 40 Reputation points

2025-08-07T16:16:31.5266667+00:00

No, I couldn't see anything inside of the VM about the disk.

Answer 1

TP 131.7K Volunteer Moderator

UPDATE: From the screenshot we can see the disk is pending detachment for some reason. The solution was to use force-detach option to detach the disk, similar to below:

For more details please see comments below.

az vm disk detach -g MyResourceGroup --vm-name new-CA-vm --name CADataTransferTemp --force-detach

Hi,

1. What Operating System is running in VM?

2. What VM size is this disk attached to? You can see size on VM's Overview blade, (e.g. Standard_D2s_v3)

3. If you navigate in portal to the VM -- Settings -- Disks, does the disk show as being Attached there? It should, but in rare cases there can be issue where resources are not properly linked.

4. Have you tried Detaching/Attaching the disk, and checking inside VM if the disk device is visible? This shouldn't be necessary, but it is quick thing to try.

Please click Accept Answer and upvote to close up this thread.

Thanks.

-TP

shijin zen 40 Reputation points

2025-08-07T17:40:49.6+00:00

1. What Operating System is running in VM?

Windows

2. What VM size is this disk attached to? You can see size on VM's Overview blade, (e.g. Standard_D2s_v3)

Standard D2s v3 (2 vcpus, 8 GiB memory)

3. If you navigate in portal to the VM -- Settings -- Disks, does the disk show as being Attached there? It should, but in rare cases there can be issue where resources are not properly linked.

Yes. Please see the screenshot attached above

4. Have you tried Detaching/Attaching the disk, and checking inside VM if the disk device is visible? This shouldn't be necessary, but it is quick thing to try.

I don't have an option to Detach/Attach
TP 131.7K Reputation points Volunteer Moderator

2025-08-07T18:01:10.9866667+00:00
Thanks, that's really helpful.

From the screenshot we can see the disk is pending detachment for some reason. That is why you don't see it inside the VM. Did you or someone else try to detach it at some point? It shouldn't get "stuck" like this, but sometimes it happens for whatever reason.

Have you tried Deallocating the VM, try to Detach via CLI command with --force-detach in Azure Shell (will probably fail and say it is "Pending"), then Start the VM again?

When the VM is Deallocated, you would use command in Azure Cloud Shell similar to below:

az vm disk detach -g MyResourceGroup --vm-name new-CA-vm --name CADataTransferTemp --force-detach

If you try different things and the disk doesn't get "unstuck" then there is no other choice than to have an Azure engineer detach it from the backend. What level Azure support plan do you have? You can check which support plan you have using link below:

https://portal.azure.com/#view/Microsoft_Azure_Support/HelpAndSupportBlade/~/supportPlans
TP 131.7K Reputation points Volunteer Moderator

2025-08-07T18:09:47.61+00:00

@shijin zen I updated my comment above to include CLI command. Please update it to correct resource group name, vm name, disk name.
shijin zen 40 Reputation points

2025-08-07T21:09:33.5133333+00:00

There are apps running on the VM. I don't think we could deallocate it? And our support plan is DEVELOPER.
TP 131.7K Reputation points Volunteer Moderator

2025-08-07T21:22:07.58+00:00

Correct, you don't want to Deallocate if it's being used. You would do it during off hours/maintenance window.

If you want to try the force detach command I posted above even with the VM running that is okay, I just thought it might have more chance of succeeding with VM Deallocated. You can try it now and then if it doesn't work give it a try again at some point when you can Deallocate first.
shijin zen 40 Reputation points

2025-08-08T16:32:41.4033333+00:00

Yes. the force detach works great. Now I can see the drive. Thanks. One more question, we can use this drive to copy files and detach from it ,then,attach to another VM, correct ?
TP 131.7K Reputation points Volunteer Moderator

2025-08-08T18:32:16.9866667+00:00

Yes, you can copy files to it, detach and then attach it to another VM. Be careful with the host cache setting when doing this, use Read-Only or None.. You don't want to write a ton of files in short period of time, and maybe they are not technically finished writing out to disk (because of caching), and you detach it.

Please click Accept Answer and upvote to close up this thread.

Thank you.
shijin zen 40 Reputation points

2025-08-10T21:33:41.4066667+00:00

Not quiet sure what you mean "be careful with the host cache setting when doing this, use Read-Only or None." can you elaborate more? thanks
TP 131.7K Reputation points Volunteer Moderator

2025-08-10T23:50:36.62+00:00

When you attach disk in the portal there is a dropdown to select host caching setting:

Set it to None or Read-only. Also, inside of the VM, disable write caching on the disk. You can do this by opening Disk Management, right-clicking on the disk, Policies tab, make sure Enable write caching on the device is unchecked:

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A disk shows on attached on VM. but Couldn't see it on VM.

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