extending data disk size in azure vm

Question

extending data disk size in azure vm

Arif Usman 496

folks. I have a virtual machine in Azure with three attached data disks. One of the disks, named obdsqllogs01, needed to be extended to 128 GB, which I have successfully completed through the Azure portal (as shown in pic)

However, after logging into the VM, I noticed it created disk2 with 2 partition and has unallocated partition. it should show on Disk 5 (LUN 1 in Azure) with unallocated partitions as a result, I'm unable to directly extend the volume (as shown in pic). Azure portal

vm screen shot diskmanager vm_partition

What is the recommended method to extend this disk at the OS level, given the presence of multiple partitions on the disk?

Aslam Mohammad 400 Reputation points Microsoft External Staff Moderator

2025-06-11T15:36:20.86+00:00

Hi Arif Usman,

I understand that you are successfully increased the disk size from the Azure portal, but within the VM's operating system, you are seeing that only 64 GB is allocated to a partition, with the other 64 GB remaining unallocated

Now, let's extend the partition to utilize the remaining unallocated space.

Right-click on that where partition you want to expand for example, Partition 2 under Disk 2.

Select Extend Volume this option will only be available if there is unallocated space adjacent to the partition.

The Extend Volume Wizard will appear.

Follow the wizard steps

When asked for how much space to add, you should see the unallocated space available (64 GB in your case).

You can choose to extend by the full amount or specify a smaller value if desired.

Click Next and then Finish.

Now verify the Disk management and verify that the size of your partition on Disk 2

if Extend volume is greyed out you can please follow this document:
https://answers.microsoft.com/en-us/windows/forum/all/extend-volume-is-greyed-out/2f93f36d-5e93-4b50-b0ff-df3f6ccc8e1a

If you have any further queries, let me know. If the information is helpful, please click on Upvote.

Thank you.
Arif Usman 496 Reputation points

2025-06-11T18:06:10.1666667+00:00

Thanks Aslam for your response, Disk 2 should be there, as soon i had extended to 128 GB at the portal, It created disk 2 and partition 2 (unallocated). I added 128 gb in LUN1 in azure portal, which suppose to be show unallocated part under disk 5 in vm...
Arif Usman 496 Reputation points

2025-06-11T18:45:35.45+00:00

I meant Disk 2 shouldn't be there
Aslam Mohammad 400 Reputation points Microsoft External Staff Moderator

2025-06-13T08:52:11.5033333+00:00

Hi Arif Usman,

Just checking in to see if you had a chance to review the response provided to your question.

Feel free to reach out if you have any further queries.

If you found the information helpful, please click "Upvote" on the post to let us know and consider accepting the answer as the token of appreciation.

Thank You.

Accepted answer

1 additional answer

Your answer

Aslam Mohammad 400 Reputation points Microsoft External Staff Moderator

2025-06-11T15:36:20.86+00:00

Hi Arif Usman,

I understand that you are successfully increased the disk size from the Azure portal, but within the VM's operating system, you are seeing that only 64 GB is allocated to a partition, with the other 64 GB remaining unallocated

Now, let's extend the partition to utilize the remaining unallocated space.

Right-click on that where partition you want to expand for example, Partition 2 under Disk 2.

Select Extend Volume this option will only be available if there is unallocated space adjacent to the partition.

The Extend Volume Wizard will appear.

Follow the wizard steps

When asked for how much space to add, you should see the unallocated space available (64 GB in your case).

You can choose to extend by the full amount or specify a smaller value if desired.

Click Next and then Finish.

Now verify the Disk management and verify that the size of your partition on Disk 2

if Extend volume is greyed out you can please follow this document:
https://answers.microsoft.com/en-us/windows/forum/all/extend-volume-is-greyed-out/2f93f36d-5e93-4b50-b0ff-df3f6ccc8e1a

If you have any further queries, let me know. If the information is helpful, please click on Upvote.

Thank you.
Arif Usman 496 Reputation points

2025-06-11T18:06:10.1666667+00:00

Thanks Aslam for your response, Disk 2 should be there, as soon i had extended to 128 GB at the portal, It created disk 2 and partition 2 (unallocated). I added 128 gb in LUN1 in azure portal, which suppose to be show unallocated part under disk 5 in vm...
Arif Usman 496 Reputation points

2025-06-11T18:45:35.45+00:00

I meant Disk 2 shouldn't be there
Aslam Mohammad 400 Reputation points Microsoft External Staff Moderator

2025-06-13T08:52:11.5033333+00:00

Hi Arif Usman,

Just checking in to see if you had a chance to review the response provided to your question.

Feel free to reach out if you have any further queries.

If you found the information helpful, please click "Upvote" on the post to let us know and consider accepting the answer as the token of appreciation.

Thank You.

Answer 1

Hi Arif Usman,

As I understand, three disks were attached to the virtual machine. One of these disks had its size extended. A new partition may have been created on that extended space, but no new disk was added it is still part of the existing disk, not a separate one

Modifying size is updating an existing disk's properties (no new LUN).

Adding disk is attaching a new disk (creates new LUN and appears as new disk in OS).

If you expand an existing disk (ex: from 64 GB to 128 GB), you are increasing the size of the existing virtual disk attached to the same LUN (LUN1 in this case).

So, Disk remains the same (ex: Disk 2, LUN 1)

No new disk is created

No new LUN is added

The partition on that disk can be extended to use the newly available space or a new partition can be created on the same disk.

It will not show up as a new disk (ex: Disk 5) or get another LUN - unless you attach a separate new disk from the VM management interface.

My Lab test:

User's image

it will create partition on the same disk (LUN1) But it does not create a new disk User's image

please refer this document:
https://learn.microsoft.com/en-us/azure/virtual-machines/windows/expand-disks

If you have any further queries, let me know. If the information is helpful, please click on "Upvote and Accept answer".
User's image

Thank you.

Answer 2

Arif Usman 496

Hi Aslam Mohammad, You have been very helpful and I am really thankful to you.

Since these vms are sql instances, I really don't want to take a risk.

So, I attach two different different disk, and map in sql to point to new created disk.

once db copied over, i had offline and detach the disk.

Again, thank you so much for responding...

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extending data disk size in azure vm

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