Every now and then I find my self with a customer who has upgraded to Windows 2012 Hyper-V but is still using VHD virtual disks. When I recommend that they convert there VHD files to VHDX I often receive the answer “Why? We don’t need files larger than 2TB”
While it is true that VHDX supports a file size of up to 64TB unlike the previous 2TB there are many more reasons to convert to the new format.
1. As already noticed the VHDX file format supports virtual hard drives up to 64TB in Size.
2. VHDX files are far less prone to data corruption as they store logs directly into the metadata structure.
This doesn’t mean that there is a log file like in SQL or Exchange servers, but there are logs being written behind the scenes.
3. VHDX files are tailored to work on modern large sector disks. This is especially important of your running a home lab in a USB disk.
4. VHDX files support larger blocks (up to 256MB) which means that dynamically expanding virtual disk don’t suffer any performance degrades compared to fixed sized disks.
5. VHDX have a logical 4K sector size wich greatly improves performance for application that work with 4K sectors, such as Exchange server.
6. Improved compatibility with ODX compatible storage arrays.
All these reasons are enough to justify the short downtime required to convert your system to VHDX. I highly urge anybody with a windows 2012 Hyper-V system still using VHD files to convert to VHDX.