VirtualBox 5: Disk Image Files (VDI, VMDK, VHD, HDD)


Disk image files on the host system are visible by guest systems as hard disks. VirtualBox redirects any request to a disk image file when a guest OS reads from or writes to a hard disk. When users create a disk image, the size needs to be denoted. This represents a fixed geometry of the virtual disk, so the size cannot be changed in the future. VirtualBox supports four types of disk image files:

Virtual Disk Images (VDI) files are used by VirtualBox as its own container format for guest hard disks. This is the format that will be used when users create a new VM with a new disk.

  • The VMDK container format is also supported by VirtualBox. This format is quite popular and is used by other virtualization software.
  • The VHD format used by Microsoft is also fully supported by VirtualBox.

VirtualBox also supports image files of Parallels version 2 (HDD format). Later versions are not supported due to a lack of documentation.

There are two ways to create a disk image (fixed-size or dynamic):

  1. When users create a fixed-size image of a certain size, another image file that is very similar in size will be created on the user's host system. Users should be aware that creating a fixed-size image may take an extended period of time. The time it takes to complete will depend on the performance of the hard disk and the size of the image.
  2.  Creating a dynamically allocated image allows users to have more flexible storage management. At first, the size of the image will be small, but will gradually grow over time each time a disk sectors is written to.
  • NOTE: This option uses less space at first, but other computer resources are needed to regularly expand the image file. When the disk is being expanded, the write operations are slower than the fixed disks. When a dynamic disk is fully expanded, performance speed is not affected.

the create new virtual disk screen.

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7/28/2016 12:40:27 PM