Hyper-v Standby Server

I recently migrated a SBS2008 server to 2012 R2 as a Hyper-V VM.  The migration went fine and all is well with the new server.

I've already migrated FSMO roles, uninstalled Exchange (they don't use Exchange) and demoted the server.

I now want to install 2012 R2 Hyper-V server on the old box to serve as a temporary host in the event of hardware failure on the current physical server.  My question is as follows:  The new server has 1 TB of storage provisioned as a virtual hard disk for the VM.  The server is only using 200 GB of that right now.  The old server only has 500 GB of space total.  Will I be able to bring the VM up on the older server with less disk space as long as total in use on new server doesn't exceed the 400 or so GB I can allocate on the old server?

Thanks in advance.
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Lee W, MVPTechnology and Business Process AdvisorCommented:
Depends.  If the VHD storing the files is fixed, then the drive size is simply too big and won't fit.  If it's dynamic, then it will be fine so long as the required space is less than the space the server has available.  Once the drive is full, the VM will be paused until more disk space is made available.

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Manojkumar RaneCommented:
Yes, you can power on or migrate the VM from new server to old server as log as VM's size not exceeds the total free space available on old server drive. Best recommendation for this situation is to configure the VHD size upto 400 GB. so that VM can be migrated on old server in the event of hardware failure.
Agree with LeeW. if the VHD(x) is dynamic and currently less than the free space on the old server it will work fine as long as it doesn't grow too much.
If it's fixed, and is therefore already larger than the free space on the old server, then no. it wont work.

I recommend reassessing the disk size you have assigned to the VM and consider if you need a 1TB virtual disk on it. If not, convert your VHD(x) to dynamic and consider amending the max size.
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Windows Server 2012

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