Virtual drive
Encyclopedia
A virtual drive in computing
is a device 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. It may also be termed an electronic disk, RAM disk
, emulated disk, e-disk, pseudo-drive, super drive, hyperdrive or memory disk.
, 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 image
s 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
and Mac OS X
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".
Some audiophile
s argue that music played from a hard drive is superior to the same music played directly from CD, 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
).
s. Applications for Mac OS X
are often delivered online as an Apple Disk Image
containing a file system that includes the application, documentation for the application, and so on. 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.
("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" or "unmounting".
. A virtual burner, by definition, appears as a disc drive in the system with writing capabilities (as opposed to conventional disc authoring programs that can create virtual disk images), thus allowing software that can burn discs to create virtual discs.
Computing
Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...
is a device that to the operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer 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. It may also be termed an electronic disk, RAM disk
RAM disk
A RAM disk or RAM drive is a block of RAM that a computer's software is treating as if the memory were a disk drive...
, emulated disk, e-disk, pseudo-drive, super drive, hyperdrive or memory disk.
Features
A virtual drive may emulate any type of physical drive, such as a hard drive, tape driveTape drive
A tape drive is a data storage device that reads and performs digital recording, writes data on a magnetic tape. Magnetic tape data storage is typically used for offline, archival data storage. Tape media generally has a favorable unit cost and long archival stability.A tape drive provides...
, key drive
USB flash drive
A flash drive is a data storage device that consists of flash memory with an integrated Universal Serial Bus interface. flash drives are typically removable and rewritable, and physically much smaller than a floppy disk. Most weigh less than 30 g...
, floppy drive, CD
Compact Disc
The Compact Disc is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage , write-once audio and data storage , rewritable media , Video Compact Discs , Super Video Compact Discs ,...
/DVD
DVD
A DVD is an optical disc storage media format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. DVDs offer higher storage capacity than Compact Discs while having the same dimensions....
/BD
Blu-ray Disc
Blu-ray Disc is an optical disc storage medium designed to supersede the DVD format. The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs. Blu-ray Discs contain 25 GB per layer, with dual layer discs being the norm for feature-length video discs...
/HD DVD
HD DVD
HD DVD is a discontinued high-density optical disc format for storing data and high-definition video.Supported principally by Toshiba, HD DVD was envisioned to be the successor to the standard DVD format...
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
RAM disk
A RAM disk or RAM drive is a block of RAM that a computer's software is treating as if the memory were a disk drive...
), or on a hard drive. Typical uses of virtual drives include the mounting of disk image
Disk image
A disk image is a single file or storage device containing the complete contents and structure representing a data storage medium or device, such as a hard drive, tape drive, floppy disk, CD/DVD/BD, or USB flash drive, although an image of an optical disc may be referred to as an optical disc image...
s of CDs and DVDs, and the mounting of virtual hard disks for the purpose of on the fly disk encryption
OTFE
On-the-fly encryption , also known as Real-time Encryption, is a method used by some encryption programs, for example, disk encryption software...
("OTFE").
Some operating systems such as Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
and Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
have virtual drive functionality built-in (see loop device
Loop device
In Unix-like operating systems, a loop device, vnd , or lofi is a pseudo-device that makes a file accessible as a block device....
), while others such as Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
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".
Backup
Disk images may be created to avoid wear-and-tear on a physical disk, such as a CD or DVD, 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.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, 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 audiophile
Audiophile
An audiophile is a person who enjoys listening to recorded music, usually in a home. Some audiophiles are more interested in collecting and listening to music, while others are more interested in collecting and listening to audio components, whose "sound quality" they consider as important as the...
s argue that music played from a hard drive is superior to the same music played directly from CD, 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
Virtual machine
A virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
).
Software distribution
After the spread of broadband, CD and DVD images became a common medium for Linux distributionLinux distribution
A Linux distribution is a member of the family of Unix-like operating systems built on top of the Linux kernel. Such distributions are operating systems including a large collection of software applications such as word processors, spreadsheets, media players, and database applications...
s. Applications for Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
are often delivered online as an Apple Disk Image
Apple Disk Image
Apple Disk Image is a proprietary disk image format commonly used with the Mac OS X operating system. The format allows secure password protection as well as file compression and hence serves both security and file distribution functions; it is most commonly used to distribute software over the...
containing a file system that includes the application, documentation for the application, and so on. 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.
Security
Virtual hard disks are most commonly used in on the fly disk encryptionOTFE
On-the-fly encryption , also known as Real-time Encryption, is a method used by some encryption programs, for example, disk encryption software...
("OTFE") software such as FreeOTFE
FreeOTFE
FreeOTFE is an open source on-the-fly disk encryption computer program for PCs running Microsoft Windows, and personal digital assistants running Windows Mobile . It creates virtual drives, or disks, to which anything written is automatically encrypted before being stored on a computer's hard or...
and TrueCrypt
TrueCrypt
TrueCrypt is a software application used for on-the-fly encryption . It is free and open source. It can create a virtual encrypted disk within a file or encrypt a partition or the entire storage device .- Operating systems :TrueCrypt supports Microsoft Windows, Mac OS X, and...
, 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" or "unmounting".
Virtual burner
A virtual disk writer or virtual burner is a computer program that emulates an actual disc authoring device such as a CD writer or DVD writer. Instead of writing data to an actual disc, it creates a virtual disk imageVirtual disk image
A virtual disk image is a file on a physical disk, which has a well-defined, published or proprietary, format and is interpreted by a Virtual Machine Monitor as a hard disk. IT administrators and software developers administer them through offline operations using built-in or third-party tools...
. A virtual burner, by definition, appears as a disc drive in the system with writing capabilities (as opposed to conventional disc authoring programs that can create virtual disk images), thus allowing software that can burn discs to create virtual discs.