Create Virtual Machine Wizard: Virtual Hard Disk

Use this page to specify a virtual hard disk for the virtual machine.

There are many ways in which Oracle VM VirtualBox can provide hard disk space to a VM, see . The most common way is to use a large image file on your physical hard disk, whose contents Oracle VM VirtualBox presents to your VM as if it were a complete hard disk. This file then represents an entire hard disk, so you can even copy it to another host and use it with another Oracle VM VirtualBox installation.

Creating a New Virtual Machine: Virtual Hard Disk

The following fields are available on this wizard page:

Create a Virtual Hard Disk Now. Creates a new empty virtual hard disk image, located in the VM's machine folder.

Enter the following settings:
- Disk Size. Use the slider to select a maximum size for the hard disk in the new VM.
- Pre-Allocate Full Size. This setting determines the type of image file used for the disk image. Select this setting to use a fixed-size file for the disk image. Deselect this setting to use a dynamically allocated file for the disk image.
  
  The different types of image file behave as follows:
  - Dynamically allocated file. This type of image file only grows in size when the guest actually stores data on its virtual hard disk. Therefore, this file is small initially. As the drive is filled with data, the file grows to the specified size.
  - Fixed-size file. This type of image file immediately occupies the file specified, even if only a fraction of that virtual hard disk space is actually in use. While occupying much more space, a fixed-size file incurs less overhead and is therefore slightly faster than a dynamically allocated file.
  For more details about the differences, see .
Use an Existing Hard Disk File. Enables you to select an existing disk image file to use with the new VM.

The drop-down list presented in the window lists all disk images which are known by Oracle VM VirtualBox. These disk images are currently attached to a virtual machine, or have been attached to a virtual machine.

Alternatively, click on the small folder icon next to the drop-down list. In the Hard Disk Selector window that is displayed, click Add to select a disk image file on your host disk.
Do Not Add a Virtual Hard Disk. The new VM is created without a hard disk.

To prevent your physical hard disk on the host OS from filling up, Oracle VM VirtualBox limits the size of the image file. But the image file must be large enough to hold the contents of the guest OS and the applications you want to install. For a Windows or Linux guest, you will probably need several gigabytes for any serious use. The limit of the image file size can be changed later, see .

You can skip attaching a virtual hard disk file to the new virtual machine you are creating. But you will then need to attach an hard disk later on, in order to install a guest operating system.

After having selected or created your image file, click Next to go to the next wizard page.