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Storage virtualization can reside in the fabric switch, an appliance or in the array's controller. Each architecture has its pros and cons.|
Fabric-based virtualization products haven't been adopted as quickly as inline virtualization appliances like IBM Corp.'s SAN Volume Controller (SVC), but they're one of the most promising storage virtualization solutions. "Fabric-based virtualization is the best technical approach to storage virtualization but it's not taking off," says Jim DeCaires, storage product marketing manager at Fujitsu.
Switch-based virtualization brings many benefits to the SAN fabric. Because the switch-based virtualization engine is out-of-band (out of the data path), there's no need for server agents, and it's the most scalable and highest performing of all virtualization architectures.
Storage virtualization sends data to physical arrays, from single or multiple vendors, as a single storage pool with the following benefit: storage can be managed as if it was on a single array, from provisioning to advanced features like replication, snapshots and mirroring between the arrays in the pool. To accomplish this, storage virtualization products map virtual volumes to physical devices; whenever a virtualized storage resource is accessed, the virtualization layer translates and redirects storage requests to the designated physical storage according
| to a mapping table.
With three primary storage virtualization architectures--in-band appliances, storage controller-based and fabric-based--the location of where virtualization should occur has been hotly debated. Each approach has its pros and cons.
This was first published in September 2008