Logical disk

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Logical disk" – news · newspapers · books · scholar · JSTOR (April 2014) (Learn how and when to remove this template message)

A logical disk, logical volume or virtual disk (VD

.

Levels

Logical disks can be defined at various levels in the storage infrastructure.

Operating system

An operating system may define

.

Storage area network

Storage area networks (SANs) consolidate inhomogeneous storage devices. As such logical disks or vdisks allow computer programs to access files stored on a SAN.^[1][2]

Storage subsystem

A hardware-level redundant array of independent disks (RAID) exposes itself to the operating system as one logical disk while the array itself consists of several disks. The operating system either does not know that the hardware with which it is interfacing is a RAID, or knows but still does not concern itself with intricate details of storage. In case of the latter, specialized management, maintenance and diagnostics software dedicated to that specific RAID may run on the operating system.

Motivation

When

, a single disk drive would be directly attached to each system, managed as a single entity. As the development of drives continued, it became apparent that reliability was a problem and systems using RAID technology evolved, so that more than one physical disk is used to produce a single logical disk.

Many modern business information technology environments use a SAN. Here, many storage devices are connected to many host server devices in a network. A single RAID array may provide some capacity to one server, and some capacity to another. Therefore, logical disks are used to partition the available capacity and provide the amount of storage needed by each host from a common pool of logical disks. The IBM SAN Volume Controller uses the term "vdisk" to refer to these logical disks.^[2]

Today, the rationale for the logical disk approach starts to be questioned^[3] and solutions that offer more flexibility and better abstraction are increasingly needed.

See also

• Storage virtualization

References