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Storage virtualization isn't a new concept, but it's getting a lot of attention lately as the top storage vendors launch next-generation virtualization wares. The vendors vary on their approaches - some put virtualization in the network, while others put it at the edge or in the array - but they all attack the same basic problem: simplifying storage management.

In traditional storage setups, the intelligence necessary to perform key storage functions such as snapshot copying, data replication and disk mirroring are handled primarily at the host or server level. Implementing virtualization, in which servers view all enterprise storage devices as one large pool of storage, means adding the software, device drivers and so on to each individual server - a situation that is notoriously tough to manage.

The first attempt to move the intelligence necessary for storage virtualization into the network came in 2000-2001 with appliances such as DataCore's SANsymphony and FalconStor's IPstor. These appliances let users pool storage while eliminating the need for drivers and licenses for each server. But this approach never really caught on, primarily because the main Tier 1 storage vendors didn't play along. "We looked at FalconStor's IPstor appliance when we put in our SAN a while back," says Bo Christiansen, IT consultant at SDC Udvikling, a Copenhagen, Denmark, financial firm. "It raised the possibility to integrate the different storage technologies under one GUI, which we liked. But there were some problems with how it worked and vendor lock-in. We decided to wait to see if we could get the virtualization without being locked in to a small vendor."

IBM became the first large vendor to embrace virtualization fully with its SAN Volume Controller (SVC), introduced in July 2003 as a network appliance or as a blade within Cisco's MDS director-level SAN switch. IBM has made considerable headway with the SVC since last August, when it added the ability to manage arrays from Hitachi Data Systems, HP and EMC; the company announced its 1,000th customer this March.

Hitachi has since rolled out its TagmaStore array-based virtualization, and Sun its StorEdge 6290 controller/array system. And EMC hit the market in May with its Invista virtualization software, which runs on Cisco, Brocade and McData director-level switches.