Q: If I use pass-through storage with Windows Server 2012 Hyper-V what are the features I lose?
A: Pass-through storage is a configuration that lets a virtual machine(VM) directly access a disk on the Hyper-V host. In this configuration, the host must have the disk in an offline state and only the VM can access the disk in pass-through configuration, making it an exclusive resource.
While pass-through was required in previous versions of Hyper-V due to limitations in the virtual hard disk (VHD) format (mostly maximum size which was 4TB), Windows Server 2012 has the new VHDX format. This not only has a new maximum size of 64TB but also delivers performance matching native disk levels, even with dynamic disks, removing the need for pass-through. If you do use a pass-through disk, you lose such key features or abilities as these:
- Create a snapshot
- Virtual Machine backup
- Storage Migration
- Hyper-V Replica
- Storage QoS
