Storage virtualisation, the reorganisation of corporate disk assets into a logical pool, will change the way firms store data, paving the way for storage to be sold as a service.

The move towards virtualisation in storage technology is set to change the way IT managers think about storage. When asked which technology they require Ã,­ storage area networks (SANs) or network attached storage (NAS) Ã,­ an increasingly common response is 'both'.

Virtualised storage aggregates many disparate disk arrays, presenting them asone logical storage pool. In effect, virtualisation combines the data management aspects and independent data transport network of SANs with the freedom to add storage when and where needed that is found with NAS systems. IT managers will therefore be able to break the link between servers, applications and storage, assigning whatever storage is required to create a convenient virtual storage system for a business process or application.

Storage as a service
This will change the way that corporate IT managers plan their storage requirements. It could also dramatically change the way that storage capacity is purchased, because it pushes users towards storage as a service, rather than as hardware to be bought and installed as required.

Some companies may take advantage of virtualisation to consolidate storage and its management functions. It will become more cost-effective to share storage, and enterprises will not necessarily require storage to be physically located in one place. This will cut costs, and because storage will not be at a single location it may reduce the risk of losing data in a disaster.

To work well, virtualisation will need the widespread use of accepted standards. These are likely to evolve as more and more storage companies are moving in the direction of IP-related technologies, giving virtual storage common ground with other areas of IT.

Virtualisation will require accepted standards for software and hardware. In other words, it will turn all storage devices into commodity products. This runs counter to the ethos of many current storage suppliers Ã,­ each company currently tends to have its own offerings and technology.

EMC is still largely accepted as the world's leading storage supplier, although Compaq likes to dispute this. In recent press reports, EMC attacked Compaq's claims of ascendancy by observing that Compaq was counting all storage units sold, including those installed in Windows servers. With virtualisation technologies, such systems could be radically different in future, in that they may not require local disk storage at all.

Virtualisation may lead some firms to view storage as just another component--a service that can be obtained from a suitable service provider.

IBM Global Services is one supplier that could be in a strong position to offer virtualised storage, because this business would fit well with its existing model. IBM Global Services wants to sell packages of IT infrastructure and services to enterprise customers. Having virtualised storage as part of its portfolio makes good business sense.

Compaq and Hewlett-Packard have recently announced plans to offer customers the option of having servers and storage on a rapidly scalable pay-for-what-you-use basis. The virtualisation approach also fits with this business model very well.

Indeed, it may be that storage virtualisation will be an essential component for these leading suppliers to succeed. Meeting firms' expectations on scalability and cost will depend on suppliers being able to switch in available storage as soon as possible, using management services that can accommodate and utilise the new capacity without interrupting end-user services.

Price and security
But virtualisation will probably have to be aggressively priced to tempt IT managers who might see risks in using such utility services, if they perceive that they will lose control of their valuable data.

However, if the suppliers can reassure customers that their data will be secure, the potential for such services is great. HP obviously believes that there is a future in this business, having moved to acquire StorageApps, a specialist in virtualisation systems, at the end of July.

EMC is still rated by analysts as one of the suppliers most likely to succeed in virtualisation. Analyst Steve Duplessie of consultancy Storage Enterprises Group, said that EMC aims to become an open systems supplier and yet still sell a lot of storage hardware, particularly at the high end.

Duplessie argued that although there may have been shortcomings in EMC's products and its strategy to date, it has the size to be a dominant force in virtualisation. However, EMC's plans differ from several of its competitors, not only because it believes that its existing high-end Symmetrix hardware will still sell Ã,­ on the basis of performance, reliability and high bandwidth Ã,­ but also because the heart of its offering, the traffic monitoring ControlCenter system, operates out-of-band.

This means that it will not have storage traffic passing through it, unlike rival products from StorageApps and DataCore. EMC argues that in-band systems provide the weak point of many virtualised solutions, because they can cause data bottlenecks, although this may only become apparent when a virtualised system is put into a large installation. The vendors of in-band systems answer this charge by saying that cacheing can improve performance, and for evidence point to the experiences of their larger customers.

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