Storage virtualization refers to the separation (abstraction) of logical storage away from the physical storage (storage hardware). This allows logical storage to be accessed without regard for the variety of hardware brands and storage device types. The logical storage is generated from the physical storage, which is combined into generic storage pools. This abstraction provides many advantages for the System Administrator including data management flexibility and cost reduction through more efficient use of the storage capacity.
A storage virtualization system presents a generic storage space composed of storage logic. A sys-admin will utilize this space as a single entry point for the data, simplifying management. The system masks the actual complexity of the storage process by mapping data to an actual physical location on the hardware behind the scenes. The preciseness with which you can control the mapping depends on the solution. In block-based storage, each block of data gets a logical unit identifier (LUN) and an offset within that unit called a Logical Block Address (LBA). Address space mapping occurs between a logical disk , also called a virtual disk (vdisk), and a logical unit that is presented via storage controllers. Virtualization software or devices use tabular mapping information called metadata to keep track of the virtualized storage.
This data can also be grouped into custom amounts of storage capacity for greater ease of management. No space is wasted in a virtualized environment because the system will automatically fill up each disk regardless of its capacity. In traditional environments you might allocate data to a disk that has more capacity than you need, but for some reason you can’t or won’t allow any more data to go on that disk and use 100% of it.
Another major benefit of storage virtualization is the ability to migrate data without disrupting the operation of a client, such as an application or website. The host only sees the logical disk so it can continue referencing that data (performing I/O) while it is mapped to a different physical location in your storage system.