The leaked Windows 8 build 7989 also contains Hyper-V 3.0 and a new virtual hard drive format, VHDX.
Both features have been uncovered by enthusiasts digging around the leaked build. Robert McLaws has detailed the support in a blog post on Monday. Windows 8 build 7989 includes the following Hyper-V 3.0 features:
- Storage
- Virtual Fibre Channel Adapter
- Storage Resource Pools
- New .VHDX virtual hard drive format (Up to 16TB + power failure resiliency)
- Memory/Processor Enhancements
- Support for more than 4 cores! (My machine has 12 cores)
- NUMA – Memory per Node, Cores per Node, Nodes per Processor Socket
- Networking Enhancements
- Hardware Acceleration (Virtual Machine Queue & IPsec Offload)
- Bandwidth Management
- DHCP Guard
- Router Guard
- Monitor Port
- Virtual Switch Extensions
- Network Resource Pools
The new VHDX format is capable of supporting disks much larger than the current 2TB restriction of VHD. Microsoft has created VHDX which is capable of supporting disks up to 16TB in size. The new format can only be used in Windows OS versions starting at Windows 8. The introduction of Hyper-V 3.0 could allow for self-contained App-V applications. McLaws also speculates that this may improve Windows Phone 7 emulator support.

Windows 8 - VHDX