With split-path technology, which is employed by EMC, intelligent switches redirect control commands to external controllers and allow read-and-write I/Os to flow from the host to the appropriate physical storage array. Companies can virtualize their storage environments using an approach like that taken by Hitachi Data Systems, where controllers assign metadata to traffic as it flows from the switch into pools.
A final method involves the use of arrays. Such vendors as HP and 3Par enable IT teams to create virtual logical-unit numbers (LUN) between the server and storage.
Fun at the block party
Yet another factor - whether a company wants to carry out virtualization at the block or at the file level - also is critical because, as Kreisa points out, there is little integration between the two. As part of a data-consolidation project, Mercury Marine deployed IBM's SAN Volume Controller appliance for block-level virtualization with Kreisa as the lead architect. Addressing the block level first let Mercury quickly alleviate its main stressors: difficulty in managing and expanding storage volumes, a lack of space on controllers, the need for a backup and restore process for expedient technology refreshes, and limited capacity for growth.
Scott Christiansen, CSO at international architectural-engineering firm Leo A. Daly, went in a different direction when he needed to consolidate data from the firm's 10 offices worldwide. As his network-attached-storage boxes expired, he replaced them with Dell's EqualLogic virtualized storage arrays that feed into Cisco Gigabit switches at each office. This allowed him to manage the storage pools as a single asset. Now, when users need space for their large AutoCAD and 3-D modeling files, he can tap into numerous resources.
Christiansen uses thin provisioning, a built-in feature of the Dell product, to automate resource allocation on his network. With thin provisioning, storage capacity is reserved only when applications write data to disk, ensuring maximum resource utilization at minimal cost.
"Traditionally, if an application needs 10GB of storage, a database administrator will ask for 40GB; the storage administrator will provision 100GB because he wants [the database administrator] out of his hair for a few months. That's 100GB earmarked for an application and won't be available to anyone else," consultant Taneja says. Thin provisioning lets IT executives such as Christiansen properly plan their capacity utilization.
Thin provisioning also saves money because it helps avoid the inherent power waste seen with today's storage, says Andrew Reichman, senior analyst at Forrester Research. "Normal provisioning leaves spindles spinning, consuming electricity and generating heat," he says.
Thanks to thin provisioning, Christiansen has been able to map data storage better and, by being able to focus on data as a whole vs. the individual store, has seen tremendous savings in technology cost and administrative time.
The pooled storage also bolsters fault tolerance, which in turn shores up disaster recovery and e-discovery plans, Christiansen says. "Storage is now one less thing that keeps me up at night. If anything goes down in one location, we can easily bring it up again in another site transparent to users," he says.
Michael Schaffer, CTO at online book, music and video exchange Alibris, praises the fault tolerance he's seen from his managed 3Par storage array, which is collocated with his network equipment at a facility in Sacramento.