If there's one thing that marketing departments in tech companies around the world are unbelievably good at, it's taking the newest and hottest technology terms and diluting them to the point that it's nearly impossible to really know what anyone is talking about anymore. Storage virtualization provides a supreme example.
These days, storage virtualization can refer to a huge swath of products and technologies, from the simplest file systems all the way up to cutting-edge storage abstraction layers that are capable of managing petabytes of heterogeneous storage spread across the world under a single coherent management framework.
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Like all forms of virtualization, storage virtualization is all about abstraction. By inserting a layer of abstraction between the storage consumer and the physical storage, you can perform a wide range of storage tricks. Taking consistent snapshots, replicating data to a redundant data center, transparently migrating data from one SAN to another, transparent backup, and zero-downtime storage failover are all examples of the incredibly handy features made possible by various kinds of storage virtualization.
Before you event think about selecting a variety storage virtualization to try and solve a problem, you need a crash course in what differentiates the various flavors.
Your basic definition of storage virtualization
In the most technical sense of the term, anything that abstracts the physical storage from the operating system that addresses it could be considered a form of storage virtualization. A simple example can be found in the file system that your hard disk is formatted with. When you open any file on your computer, it performs a lookup in your file system's file allocation table that resolves to the logical blocks on your hard drive that make up the file. That table is essentially a database containing the necessary metadata to link a given file name that you might recognize to the actual location of the files on the physical media that the hardware will recognize.
That may seem like a simplistic place to start when talking about such a complex topic, but that same model plays out no matter what level of storage virtualization you may be talking about. It's just an issue of scope and complexity.