Expanding volume on basic disk on Hyper-V replicated cluster

Jozef Woo
Jozef Woo used Ask the Experts™

I expanded a disk for a VM in Hyper-V. Now I need to expand the volume but it has no contiguous space and it's a basic disk. Windows suggests to convert it to a dynamic disk but I heard that it might not be such a good idea to convert it to a dynamic disk.

Is it true that there is a risk in converting it to dynamic? And if so, how can I proceed? The volume needs urgent expanding.

Thanks for your help!
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Top Expert 2014
If it is just a data disk then dynamic disks should be OK, if it has the OS/boot/system on it then that would be a waste of time because dynamic disk spans aren't allowed since a defrag may push boot code onto the second disk and then obviously it could not get that file to boot from.

You can always take the VM offline and use Bootit BM, gparted or EaseUS partition manager or any of the other offline partition managers to shuffle the data about to make it contiguous.
kevinhsiehNetwork Engineer
Did you partition the VHDX? That's a big no-no, because you can't expand partitions if there is another one after it. There is no reason to partition a VHDX. If you need more than 1 drive letter, use more than 1 VHDX. Partitioning is only needed for physical disks.

Can you post a screenshot of what you see in disk manager? My guess is that you partitioned, and you want to expand a partition like C, when you also have a D partition on same disk. In that case, I recommend copying the later partitions each to their own VHDX. That will free up the needed space to expand your partition.

I recommend that you never ever make a dynamic disk. Too many utilities, backups, and recovery options don't work with dynamic disks.
Philip ElderTechnical Architect - HA/Compute/Storage
If there are two partitions in the one VHDX then the process is simple:
 1: Create and bind a new VHDX to the VM
 2: Set up a partition and give it a drive letter
 3: Either run a restore of the data volume from backup or direct copy content making sure to include NTFS permissions
 4: Once ready, flip the shares over to the newly restored or copied data
 5: If there's a time disparity between restore and go-live use a utility like BeyondCompare to run a final sync

Once the above steps are complete, delete the second data partition and expand the guest OS partition as needed. Or, shrink the VHDX.

Make sure to reconfigure the backup software if needed once the above is done.
Jozef WooSystem Engineer


Thank you all for the valuable inputs. I will proceed to create a new VHDX and "migrate" the fileshare to this VHDX. Just have to find out how to do that with the least user impact but the problem stated above was solved as such!
Philip ElderTechnical Architect - HA/Compute/Storage

Once everything has been sync'd over schedule an outage of about 5 minutes.

Remove the existing shares then recreate them on the newly set up folders with the data in them.

NOTE: Make sure the base folder permissions are set properly _before_ running the sync job!

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