Virtual disk and virtual drive

Virtual disk and virtual drive are software components that emulate an actual disk storage device.

Virtual disks and virtual drives are common components of virtual machines in hardware virtualization, but they are also widely used for various purposes unrelated to virtualization, such as for the creation of logical disks.

Operation

A virtual drive is a software component that emulates an actual disk drive, such as an optical disc drive, a floppy disk drive, or a hard disk drive. To other programs, a virtual drive looks and behaves like an actual physical device.

A virtual disk may be in any of the following forms:

• Disk image, a computer file that contains the exact structure of an actual drive
• Logical disk (also known as vdisk), an array of two or more actual drives that cooperatively act like a single device
• RAM disk, which stores its data in random-access memory instead of on a physical drive

Uses

In hardware virtualization, virtual machines implement virtual drives to emulate the behavior of an actual machine. A virtual machine needs one virtual drive and one disk image to start up. More virtual drives are added as needed.

Virtual optical drives are used on actual machines to transfer the contents of the optical disks onto the hard disk drives. Doing so helps resolve the problem of the short life span of CDs and DVDs and allows taking advantage of the faster data transfer rate of hard disk drives. However, virtual optical drives are also used for software piracy: Early computer games used disc existence verification to ensure licensed use. The StarForce copy protection scheme attempts to thwart disc virtualization. Some video games, however, have adopted online product activation instead.

See also

• Floating drive
• Storage virtualization
• Comparison of disc image software