In storage virtualization

Storage Virtualization

Storage virtualization or storage virtualisation is a concept and term used within computer science. Specifically, storage systems may use virtualization concepts as a tool to enable better functionality and more advanced features within the storage system.Broadly speaking, a 'storage system' is...

, virtual disk, or vdisk, is a virtual logical disk

Logical disk

A logical disk is a device that provides an area of usable storage capacity on one or more physical disk drive components in a computer system. Other terms that are used to mean the same thing are partition, logical volume, and in some cases a virtual disk .The disk is described as logical because...

 or volume to which a host or application performs I/O

I/O

I/O may refer to:* Input/output, a system of communication for information processing systems* Input-output model, an economic model of flow prediction between sectors...

 operations. Generally provided by a storage virtualization device and applicable mainly to Fibre Channel

Fibre Channel

Fibre Channel, or FC, is a gigabit-speed network technology primarily used for storage networking. Fibre Channel is standardized in the T11 Technical Committee of the InterNational Committee for Information Technology Standards , an American National Standards Institute –accredited standards...

 storage area network

Storage area network

A storage area network is a dedicated network that provides access to consolidated, block level data storage. SANs are primarily used to make storage devices, such as disk arrays, tape libraries, and optical jukeboxes, accessible to servers so that the devices appear like locally attached devices...

 (FC SAN) infrastructures. Presently, the term vdisk is used in HP EVA

HP StorageWorks

In computing, HP Storage , a portfolio of Hewlett-Packard storage products, includes online storage, nearline storage, storage networking, archiving, de-duplication, and storage software. HP has developed many industry-first storage technologies to simplify network storage...

 disk arrays and in IBM SAN Volume Controller

IBM SAN Volume Controller

In computer data storage, the IBM SAN Volume Controller is a block storage virtualization appliance that belongs to the IBM System Storage product family. SVC implements an indirection, or "virtualization", layer in a Fibre Channel storage area network .- Architecture :SVC is always deployed as a...

.

The disk is classed as virtual due to the way it is mapped to the physical storage capacity it represents. In most virtual storage systems a meta-data mapping table is held which translates the incoming (virtual) disk identifier, and LBA (logical block addressing

Logical block addressing

Logical block addressing is a common scheme used for specifying the location of blocks of data stored on computer storage devices, generally secondary storage systems such as hard disks....

) to a physical disk identifier and LBA.

The virtualization granularity depends on the implementation. Some virtualized systems simply provide what may be thought of more as disk aggregation

Disk aggregation

Disk aggregation is the process of combining more than one logical or physical disk drive into a larger logical disk drive.This is done for various reasons :* creating a single logical disk with a capacity larger than any of the available physical disks...

and so the granularity is a physical disk itself. True virtualization systems actually break down the physical disks into smaller 'chunks' or extents. This can provide a performance benefit by spreading a single virtual disk across many physical disks - therefore getting more concurrent access than a non-virtualized system.

V-disc is also a record label of musical tunes especially recorded for soldiers of the World War II.