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Growth in teleradiology studies spurs SAN upgrade

John Moore | Oct. 29, 2013
As a virtual radiology firm saw its workload nearly triple, storage performance suffered. That, in turn, impacted the underlying database, to the point that maintenance jobs overlapped. Rather than rewrite the database, Virtual Radiologic opted to upgrade it SAN -- and saw latency drop dramatically.

At vRad, storage performance problems impacted its SQL databases. Williamson says databases were getting slow and maintenance jobs were taking longer. The situation deteriorated to the point where database maintenance jobs overlapped and didn't always complete successfully, he notes.

The teleradiology operation had reached a key decision point: Rewrite databases to run on a slower SAN or deploy a new SAN. The company opted for the latter choice, rolling out Nimble CS460 GX2 hybrid storage arrays and the storage vendor's SmartStack for Business-Critical Applications. The latter is a converged infrastructure reference architecture, which includes Nimble's CS-Series arrays, Cisco Systems' Unified Computing Systems B-Series blade servers and VMware vSphere 5.1

Taking this storage approach resulted in a 5x reduction in write latency and a 25x reduction in read latency, according to vRad.

Jacob Wilde, lead systems engineer at vRad, says Nimble's take on shared SAN storage marks a departure from other storage vendors. Storage providers traditionally add more disk to get more performance out of a SAN, he says. Nimble, in contrast, achieves performance through CPUs, solid state drive caches, RAM and the Nimble file system.

"Nimble eliminates spindle count as being the traditional performance bottleneck for storage performance," Wilde says. He also notes that customers can further expand performance with version 2.0 of the Nimble operating system, which lets customers take advantage of the performance of up to four arrays in a scale-out cluster.

The teleradiology company can use fewer drives on the Nimble SAN compared with its former storage system, as it now obtains more IOPS per drive. In testing, the Compellent SAN had 114 x 15,000 rpm NL drives and 42 x 7,000 rpm NL drives, while the Nimble SAN had 25 x 7,000 rpm NL drives, according to Wilde. Using the SQLIO benchmarking tool, vRad found the Compellent SAN averaged 84 write IOPS per drive versus 820 on the Nimble SAN.

New SAN Also Meant No 'Massive Database Rewrite'
Performance isn't the only story, however. The overhaul also let vRAD avoid an expensive technical exercise. The SAN, Williamson says, "prevented us from going through a massive database rewrite effort, which would have been very costly from a personnel perspective." He estimates it would have taken vRad's development group six months to perform the rewrite at cost of at least $100,000.

The SAN has other cost-saving implications, too. The company has been able to virtualize more servers in light of the SAN's improved speed. "There were apps and servers we were never able to virtualize because local disk in the server was faster than the SAN performance we were getting," Williamson says.

The company's development environment runs about 350 servers, all of which are virtualized. On the production side, about 250 out of 350 servers are now virtual machines. The virtualization program continues, Williamson says: "We are virtualizing as many servers as we can."


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