Virtual drive
A virtual drive is the functional replication ( emulation ) of a drive including a data carrier or removable medium. In most cases it is an emulation of a CD and / or DVD drive . Even floppy drives or other removable media can be emulated. Virtual drives do not exist as hardware, but from the user's point of view they are addressed in the same way and function in the same way as physical drives.
In the following, the main application of a virtual CD or DVD drive will be discussed; but much can be transferred to other types of storage in the same way.
Basics
A virtual drive is a pure software complex that makes the original hardware (drive including CD / DVD) superfluous: the data are located on the hard drive after an installation process - which is fundamentally required - and a 1: 1 copy of the data CD has been created of the computer; they can also be made accessible to several computers via a network. In principle, the content of any CD or DVD can be made accessible in the form of a virtual drive; however, this is not as easy and quick as inserting another data carrier into the drive drawer.
Access to file images
The file image of a CD or DVD is transferred to a hard disk in a special form - usually as a so-called ISO file (due to the different nature of the data management of a hard disk, it is not a simple copy in the strict sense). The files on a virtual drive cannot be read by any common file management program (e.g. “ Explorer ” under Windows or “ Konqueror ” under Linux ); this is only possible through special programs (see below). After the installation, however, access via the partition designation ( drive letter or volume name ) is possible and the user is no longer formally different from using the original data on CD or DVD.
Programs that provide a virtual (CD / DVD) drive under Windows are e. B .:
CDemu is ideal for Linux . However, ISO images can also be mounted here without an additional program ; this command can be used (with the necessary access rights ), for example:
mkdir -p /mnt/iso && mount -t iso9660 -o loop=/dev/loop0 /test.iso /mnt/iso
In some distributions ( e.g. Debian ) it is sufficient to just -o loopenter the option .
Advantages and disadvantages
The advantage of data storage on a hard disk is basically that it achieves significantly shorter access times . (Magnetically stored data is read from a hard disk by its drive mechanism - namely the read / write head - much faster: It usually takes less than 10 milliseconds to drive to a data track . On the other hand, the completely different head mechanics of an optical drive - also because of its larger mass - a much greater inertia when moving the laser and lens system back and forth.)
This results in another advantage for virtual drives in battery-powered notebook computers: Since optical CD and DVD drives also have a significantly higher power consumption compared to magnetic data storage on hard drives, a virtual drive contributes to this, which is often already scarce Increase battery life accordingly.
The main disadvantage of a virtual (CD or DVD) drive is that storage space is lost as the entire content of a CD or DVD, e.g. B. in the form of an ISO file must be copied to the hard drive. Conflicts with other drivers can also occur, which means that the real drive no longer works properly (e.g. when burning).
Differentiation: virtual and logical drives
Although it is also possible to combine several physical hard disks into a network, which can then be addressed as a single storage unit, such a hard disk network is rarely referred to as a virtual drive - the term logical drive has largely become established for this. Physical hard disks and their individual partitions can be logically connected to one another in different ways (e.g. also to form so-called RAID systems), but they are not actually considered to be “virtual” drives, even if they are externally performed by the user can be addressed in the same way.