One of my favorite changes in Win8/WS2012 is the new .VHDx file format, sometimes referred to as VHD 2.0 format.
- Overcoming the VHD limitation of 2TB, VHDx can be as large as 64TB
- The improved internal alignment lends itself well to being stored on disk with 4KB sector size
- Can be configured to have 4KB sectors even if the physical storage has a standard 512byte sector size
- Far better performance for dynamic and differencing disks
- Supports TRIM for sector reclamation (can give back space when not in use by unmapping virtual sectors from the physical sectors that were backing them)
You can use Windows PowerShell to convert from one format to another (Convert-VHD).