I can't create new or expand existing VHD in Hyper-V


I've been trying to add a new VHD to an existing VM but am experiencing problems. when I try to add the new disk the Hyper-V manager hangs in the creating new disk step. I've then tried to expand an existing disk and then suffers a hang when the Hyper-V manager is discovering the current disk I want to expand. I've made sure there is enough free space available where I want to create the VHD. I've also tried this using a different managing machine and the 5nine Hyper-V manager but am experiencing similar problems.

The VM who's disks I'm trying to modify is a SBS 2011 and is the only DC and DNS on the network. The Hyper-V machine is a Server 2012 Core.

Any suggestions on what might be wrong?

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Cliff GaliherCommented:
Are you sure it is hanging? If the VHD being created or expanded is static. The system actually writes every sector at creation or expansion time. That can take quite awhile. Patience...
joebilekAuthor Commented:
Considering it's a server in active production the most I have given it is about 60 minutes for creating a 50 GB disk. What would be a reasonable amount of time to wait?

Having created disks in other Hyper-V environments I'm not used to this step taking more than a few minutes.
Cliff GaliherCommented:
It is all about I/O. Trying to expand 50GB on 7.2k disks in RAID5 while other VMs are running on the same spindles? 60 minutes is a pipe-dream. In all but test labs with dynamically expanding disks is "a few minutes" realistic. So how long it should take...I can't say. I don't know the server or workloads. But I can guess by your response that your expectations may be a bit... aggressive.
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joebilekAuthor Commented:
I'll try a nightly update giving it plenty of time to create a new 50 GB disk and will return here if there are further problems.

Please note though that I can see the file having been created at full size on the Hyper-V Core machine after just a minute or so.
Cliff GaliherCommented:
That's just an NTFS journal entry. It takes almost no time. But since the virtual disk is static, the system still has to write the VHD information to the actual areas allocated, and that takes much longer.

Think of it like renting a storage unit. The space is yours the moment you sign the contract. And you can look at the contract and see the size of the space you rented. But if you are going to store stuff, you have to go to the unit and install shelving. The shelves will start empty, but setting up shelves still takes time.

The VHD may not hold data, but it still has a structure and format that mist be written, block by block.
joebilekAuthor Commented:
I'll try it out and will let you know if giving it more time will solve it.
joebilekAuthor Commented:
Created a new dynamic vhd instead which was done in seconds and used it instead.

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joebilekAuthor Commented:
Solved our problem
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