VDI vs. VHD vs. VMDK

Virtual Disks

Virtual Disks are files or sets of files that appear to the operating system as physical disks. Their data can be stored locally or remotely. Virtual disks are often used to run different operating systems within the operating system.

There are multiple different file types for virtual disks including VDI, VHD, and VDMK.

File Types

These files have several differences and similarities:

1. VDI was developed for VirtualBox, VHD was developed by Microsoft for Virtual PC, and VMDK was designed for VMware. VirtualBox, Virtual PC, and VMware are all virtualization software designed to run these virtual disks.
2. Virtual Box supports all three file types. VMware, on the other hand, only offers direct support for VMDK, which makes it the most widely compatible of the three.
3. All three file types are interconvertible, so they allow portability to other virtualization software.
4. All three allow dynamically allocated storage, but VMDK additionally supports splitting storage files less than 2 GB each, which may help overcome low file size limits.
5. While there is no official benchmark test for all three file systems, there is theoretical reason to believe that VDI performs better than VHD. This has been backed by an unofficial test, which proved that VDI is faster than VHD. Another unofficial test showed significantly better speeds in VMDK than VDI.
6. A user-run test also determined that VDI has fairly smaller file sizes than VHD.
7. VMDK also supports incremental backups. Incremental backups copy only the data that was changed after the previous backup instead of copying all of the data. This feature makes backing up data more efficient and quicker as compared to VHD and VDI, which do not support incremental backups.