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With more and more information being demanded of companies in nearly every sector of business, the ability to store and retrieve data is of paramount importance. For Business Continuity, digital storage represents a means of recovering from unforeseen setbacks. With such copious amounts of data being stored routinely, a method of easy retrieval is in significant demand. An emerging technology that delivers solutions for this very issue is Storage Virtualization.
Storage virtualization is a new way to store data while simplifying its presentation 1. It involves the use of a virtualization software client providing a “layer of abstraction” between the data’s physical address and its logical address. In other words, the user’s view of the data layout is not necessarily reflective of the literal allocation on the storage devices. The software client informs the user on a particular file’s location as though it were grouped together with related files, while in reality, they may be located on completely separate disc arrays 2!
You may wonder, what good is it to be able to view files as though they were logically grouped together? As it turns out, storage virtualization can save you money on disc space and man hours. The idea behind storage virtualization is to shield users and administrators from the complexity of the storage environment. After all, if there seems to be practically no rhyme nor reason to the random splattering of files across the storage servers, why should the users be troubled by it?
The more complex the data allocation, the more your management costs will be. That’s why storage virtualization is so advantageous. It allows the system managers to
understand what data they have without troubling them with the underlying complexities of the layout. With that in place, you don’t have to pay managers extra to unravel those complex systems.
Another way that storage virtualization saves money is by allowing a company to more efficiently use their data capacity. By not having to worry about keeping related files grouped together on a particular disc array, a manager can completely utilize a single storage unit with heterogeneous (composed of different types of) data. It isn’t important to make sure that all related files are group together physically 3. If there is room on a storage device, you can shove your next batch of data on there and think no more about it!
So now that we have an idea of why this technology might be useful, how does it work? When a file is saved and committed to storage, it is recorded physically on a storage medium of some kind. When storage virtualization is being implemented, mapping location information is created and stored along with it. That information, called metadata, is saved in a mapping table which attaches a logical address to the physical address in the storage device.
What this indicates is that there are two ways to define a files location with storage virtualization. There is, of course, a physical location and there is a logical location as well. The physical location refers to the literal device upon which the information is stored. The logical location is some illustrative representation that strategically groups files in some understandable and likely order. The mapping table is the part of the virtualization client that matches up the physical with the logical, and delivers an understandable and likely allocation schema to the user.
A generic example of storage virtualization in action might go a little something like this: a company that has implemented virtualization has a group of related files mapped together so that they appear grouped as a logical unit (LUN) on their storage array. In reality, these files aren’t really grouped together, in fact, they might be dispersed haphazardly across the storage devices in logical block addresses (LBA’s) wherever the virtualization client could fit them.