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Storage virtulisation unmasked

Storage virtulisation unmasked

Virtualisation has become the tabloid story of the data storage industry - hot, controversial and everywhere. BRETT WINTERFORD tries to separate the virtual from the reality.

Virtualisation is a concept created by the data storage industry to describe new ways of masking the complexity of storage environments. It's about managing all of your various physical storage devices - be they RAID arrays, disk drives or tape drives - as a single pool of storage.

The concept has seen a good deal of hype in the tech press. In the words of one industry guru, storage virtualisation has become "centre square in buzzword bingo". And for good reason: implemented in its ideal form, storage virtualisation lowers IT management costs and makes life considerably easier for administrators. But the problem for resellers looking to invest their skills in virtualisation is that you are likely to get a different answer on how to go about it from just about every vendor you talk to.

Traditionally, storage assets have been attached and assigned to individual servers to cater for specific applications. Every server typically had its own attached storage.

"You may have had two servers for two different applications - one with 10 per cent utilisation, one with 100 per cent, but you still had to buy more storage for the device that was running out of space," Network Appliance marketing director, Mark Heers, said.

DIPPING INTO THE POOL

A far more efficient use of resources is to have a single pool of storage that all servers can share. Virtualisation refers to the abstraction layer that enables these disparate storage resources to appear as one virtual pool in a management console.

"With virtualisation, you are able to just use the total pool until it is full, and add more disk as you need it," Heers said.

Virtualisation has many benefits for IT administrators. At the physical level, it addresses the disparity between the actual storage capacities of devices and the requirements of individual applications. Typically, storage hardware has a greater capacity than what is required by an individual application.

"Before virtualisation, you might have purchased three years worth of your storage needs for the life of a project," Symantec technology specialist, Mark Read, said. "A lot of the capacity would just be sitting there, consuming power, taking up space in the data centre until such time as it would be needed. With virtualisation, somebody else within the organisation might be able to use that capacity until such time as you need it."

Virtualisation provides administrators with a macro view of a single virtual resource, masking the complexity of the many physical assets that make up that resource. Ideally, it should enable administrators to migrate data from one system to another without too much staff involvement.

Analyst group, Gartner, suggests that without virtualisation, one administrator is able to manage up to around 300GB of data; whereas in a well-executed virtualised environment, that person could manage up to 2TB.

"People are the most expensive asset in a data centre," Enstor managing director, Terry Semple, said. "Virtualisation can lead to enormous cost savings from that perspective. With the proper set-up, you could manage five or ten times the same capacity of storage with the same amount of people." It also allows organisations to define policies which link the importance of data with the performance and cost of the medium it is being stored on. Using tools that analyse types of data and their value to the business, data can be allocated in a tiered fashion. Critical data can be stored on high performance, expensive disk while data that has become less critical is stored on cheaper media.

Examples of such policies might include transferring data that has not been used or accessed for six months to cheaper disk, or permanently storing the files of high-ranking executives on high performance disk. These policies can also determine where data is stored according to file type - for example, bulky video files might be considered too expensive to use on high performance disk and be relegated to cheaper media.


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