As a virtual disk is called the functional simulation ( emulation ) of a drive including a disk or removable media. In most cases, it is the emulation of a CD and / or DVD drive. Also, floppy drives or other removable media can be emulated. Although Virtual drives do not exist as hardware, but are addressed from a user perspective as well and are analogous to the physical drives.
Below are details especially on the main application of a virtual CD or DVD drive; much but can be applied by analogy to other types of memory.
A virtual disk is a pure software complex, which makes the original hardware (drive including CD / DVD ) superfluous: The data are for a - basically required - installation process and creating a 1:1 copy of the data CD to the hard drive of the computer; they can be made available to multiple computers over a network, however. In principle, the contents of each CD or DVD will be made available in the form of a virtual drive; but that does not happen as easily and quickly as inserting a different disk in the drive tray.
Access to create images
The file image of a CD or DVD is in a special form - usually transmitted as so-called ISO file to a hard disk (due to the different nature of the data management of a hard drive is not in the strict sense a simple copy). The files in a virtual disk are also not a common file management program (eg, the "Explorer" on Windows or " Konqueror" under Linux) to read; this is only possible through special programs ( see below). After installation, however, the access on the partition name ( drive letter or volume name) is possible and exists for the user in a formal sense no difference to use the original data to CD or DVD.
Programs that are put under a virtual Windows ( CD/DVD- ) drive available, for example:
Under Linux CDemu offers. However, ISO images, you will also be suspended without an additional program, this can ( with the necessary access rights) for example, this command can be used:
Mkdir -p / mnt / iso && mount-t iso9660 -o loop = / dev/loop0 / test.iso / mnt / iso In some distributions (such as Debian), it is sufficient to enter only the option "- o loop ".
Pros and Cons
The advantage of storing data on a hard disk is basically in reaching a much shorter access times. ( The reading magnetically stored in the repository from a hard disk is performed by the drive mechanics - namely the write - much faster: to approach a data track, typically less than 10 milliseconds other hand, requires the completely different head mechanics of optical drive - even if only because of their greater mass. - a much greater inertia on the outward and forth movement of the laser and lens system ).
This gives a further advantage for virtual drives results with the battery powered laptop computers: Since the optical CD and DVD drives to hard drives also have a significantly higher power consumption compared to the magnetic data storage, contributes a virtual disk to the often anyway scarce battery life should be increased accordingly.
The disadvantage of a virtual (CD or DVD ) drive consists essentially in the fact that sufficient memory is lost because the entire contents of a CD or DVD, for example in the form of an ISO file must be copied to the hard disk. Also conflicts with other drivers can occur, which means that the real drive is not working properly (for example, when burning ).
Demarcation: virtual and logical drives
Although it is also possible to have multiple physical disks together to form a composite, which can then be addressed as a single storage unit, however, such a disk composite is rarely referred to as a virtual drive - that's the term has largely prevailed logical drive. Although physical disks and their partitions are logically connected to each other in different ways (eg also called RAID systems ), but they do not apply in the real sense as a "virtual " drive, even if from the outside by the user in the same way be addressed.