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Wanted: Modular growth
John Wunder, director of IT at Magnum Semiconductor in Milpitas, CA, began looking for a VTL after an acquisition caused a seven-fold increase in the amount of data the company needed to back up every night. The 21TB of data was too much to back up within the company's two-hour nightly backup window.

He considered purchasing a deduplication appliance from Data Domain that would dramatically speed the backup process by storing only unique changes to the data. However, at the time of his selection, Data Domain packaged its appliance with a set amount of storage, "so if we wanted to add another appliance it would" create another island of storage, he says.

EMC and NetApp take a similar approach, says Whitehouse, forcing a customer to do a "forklift" upgrade of their entire system or buy another VTL just to get a comparatively small additional amount of capacity. That can result in "VTL sprawl," she says, with "lots of different boxes, each of which has to be managed independently."

Using a Quatrio Pivot 300 VTL running Diligent's ProtecTier data deduplication software, Wunder says he can meet his expected 50% annual growth in storage needs by buying another disk array every year and another server every two years. "If I'm wrong on [the amount of] data growth, I'll just escalate" those expansion plans, he says. Each expansion "is

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less than $20,000 a pop, a small enough amount of money so I can double, triple or even quadruple the size" of the VTL if needed, he adds.

Wunder uses the VTL to store data before moving it to a Quantum Corp. LTO-3 tape library for long-term offsite archiving and DR. This will save the company $300,000 over four years vs. the cost of building and maintaining a tape library large enough to meet its future needs, he says.

Wunder wishes he could have changed his company's centralized approach to storing data on one NAS filer in one file system (which he inherited from his predecessors). "If I just had this 21TB stored across three or four" storage systems, he says, he could back up data to multiple VTL servers at once, further reducing his backup window.

A number of vendors are combining 4Gb/sec Fibre Channel with multithreading capabilities to do exactly that, says Whitehouse. Sepaton, for example, "can stack any of a number of their nodes in one solution," she says. Each node "might have two or four Fibre Channel connections, so the scalability becomes easy to map out."

Magnum Semiconductor's Wunder strongly advises users to build extra capacity into their VTL arrays--"a minimum of double of what you need [now]," he says--to allow enough extra space to accommodate not only regular backup storage, but extra space to test applications and DR plans. "I can't test if I don't have a staging area," he says.

This was first published in August 2008

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