Microsoft will be introducing a new file format (VHDX) for virtual hard disks as part of Hyper-V in Windows Server 2012. The original format (VHD) has been around for many years, the new format provides a host of additional benefits.
At a glance, the new format supports up to 64 terabytes, so this will help in situations where large volumes of data need to be catered for. The sector alignment and increased block sizes mean disk utilization is improved, and makes more efficient usage of modern disk drives. There’s also a logging mechanism to reduce the impact of power outages.
Here’s the main info from Technet:
 The main new features of the VHDX format are:
- Support for virtual hard disk storage capacity of up to 64 TB.
- Protection against data corruption during power failures by logging updates to
the VHDX metadata structures.
- Improved alignment of the virtual hard disk format to work well on large sector
The VHDX format also provides the following features:
- Larger block sizes for dynamic and differencing disks, which allows these disks to
attune to the needs of the workload.
- A 4-KB logical sector virtual disk that allows for increased performance when
used by applications and workloads that are designed for 4-KB sectors.
- The ability to store custom metadata about the file that the user might want to
record, such as operating system version or patches applied.
- Efficiency in representing data (also known as “trim”), which results in smaller file
size and allows the underlying physical storage device to reclaim unused space.
(Trim requires physical disks directly attached to a virtual machine or SCSI disks,
and trim-compatible hardware.)
I’m going to be writing more about the new edition of Hyper-V in coming articles. Check back for more, including the following:
- Hyper-V Replica
- Expanded processor and memory support
- Dynamic Memory Improvements
- Network adapter improvements