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A virtual drive in computing is a drive that to the operating system appears to be an ordinary physical disk drive, with disc images substituted for disc reading hardware through the use of software called a disk emulator.

A virtual drive may emulate any type of physical drive, such as a hard drive, tape drive, key drive, floppy drive, CD/DVD/BD/HD DVD or a network share among others. An emulated drive is typically created either in RAM for fast read/write access (known as a RAM disk), or on a hard drive. Typical uses of virtual drives include the mounting of disk images of CDs and DVDs, and the mounting of virtual hard disks for the purpose of on the fly disk encryption ("OTFE").

Some operating systems such as Linux^[1] and Mac OS X^[2] have virtual drive functionality built-in (see loop device), while others such as Microsoft Windows require additional software.

Virtual drives are typically read-only, being used to mount existing disk images which are not modifiable by the drive. However some software provides virtual CD/DVD drives which can produce new disk images; this type of virtual drive goes by a variety of names, including "virtual burner".

Contents 1 Uses 1.1 Backup 1.2 Enhancement 1.3 Software distribution 1.4 Security 1.5 Remote data storage 2 Virtual Burner 3 See also 4 References

[edit] Uses

[edit] Backup

Disk images may be created to avoid wear-and-tear on a physical disk, such as CD or DVD or ISO files, with the disk image mounted in a virtual drive when needed. Similarly, disk images can provide a backup copy of physical disks, in case the original is damaged, lost or stolen.

[edit] Enhancement

Using disk images in a virtual drive allows users to shift data between technologies, for example from CD optical drive to hard disk drive. This may provide advantages such as speed and noise (hard disk drives are typically four or five times faster than optical drives,^[3] and also quieter). In addition it may reduce power consumption, since it may allow just one device (a hard disk) to be used instead of two (hard disk plus optical drive).

Some audiophiles argue that music played from a hard drive is superior to the same music played directly from CD,^[4][5] due for example to lower data error rates.

Virtual drives may also be used as part of emulation of an entire machine (a virtual machine).

[edit] Software distribution

After the spread of broadband, CD and DVD disk images became a common medium for Linux distributions^[1]. Online data and bootable recovery CD images are provided for customers of certain commercial software companies.

Disk images may also be used to distribute software across a company network, or for portability (many CD/DVD images can be stored on a hard disk drive). Disk images may also be needed to transfer software to machines without a compatible physical disk drive.

[edit] Security

Virtual hard disks are most commonly used in on the fly disk encryption ("OTFE") software such as FreeOTFE and TrueCrypt, where an encrypted "image" of a disk is stored on the PC. When you enter the disk's password, the disk image is "mounted", and made available as a new drive letter on your PC. Files written to this virtual drive are written to the encrypted image, and never stored in cleartext.

The process of making such an encrypted disk available for use is called "mounting", the process of removing it is called "dismounting"

[edit] Remote data storage

See also category: Cloud storage

Virtual drives may also be used to facilitate access to remote data storage across networks, for example via network shares mounted as local drives, or the mapping of FTP and SFTP sources as virtual drives. This remote data storage may be across an organisation's internal network, or across the internet, where a variety of providers offer what is known as "cloud storage". Cloud storage involves the delivery of data storage as a service, including database-like services, often billed on a utility computing basis, e.g., per gigabyte per month.^[6]

[edit] Virtual Burner

This section requires expansion.

A virtual CD burner is a device driver that emulates a writable CD/DVD drive. It appears as another drive in the system with writing capabilities. When information is written to the drive, it creates an ISO Image representation of the CD that would, under normal circumstances, be physically created. ISO images can be compressed into .CSO images.

A virtual CD burner can be used by any CD burning/writing software, and create an image which can be later mounted as a virtual drive. Most CD writing software does not provide CD burner capability, instead providing a manual option within the program such as "Create Disc Image" or "New ISO File".

Software with virtual burner capabilities include Virtual CD which allows CD-R and DVD-R, and Phantom Burner which allows CD-R and DVD-RW emulation.

[edit] See also

• subst
• Comparison of ISO image software
• List of ISO image software
• CD/DVD copy protection

[edit] References