The choice between buying a hybrid flash and all-flash array (AFA) usually comes down to whether the all-flash system gives enough of a performance bump to justify the extra cost.
National Information Solutions Cooperative (NISC) systems engineering team lead Tige Vollrath recently put the hybrid Nimble Storage array up against a leading AFA and noticed little performance difference, so he stuck with his hybrid setup.
NISC, a software development company that provides applications for telecommunications and utility companies, installed Nimble Storage hybrid arrays in 2013 at data centers in Mandan, North Dakota and Lake St. Louis, Missouri. The organization has had two clustered Nimble CS460 arrays at each site. Each Nimble Storage array has an all-flash shelf and hard disk drive capacity expansion shelf for a total around 140 TB of disk capacity and 20 TB of flash cache at each location.
Rather than sell an all-flash array, Nimble offers the all-flash expansion shelf for customers who want to add solid-state drives (SSDs) without taking up hard disk drive slots. NISC upgraded its flash and hard disk drive capacity last year in Lake St. Louis and planned to do the same this year in Mandan. However, before the second upgrade, Vollrath said he wanted to determine if an AFA would give him better performance. Vollrath said the NISC brought in an array from a "well-known all-flash vendor" that he declined to identify for a proof of concept.
"There was a lot of buzz about all-flash arrays," he said. "We felt that we needed to exhibit due diligence and evaluate all-flash systems to see what the impact would be of all-flash versus a hybrid solution like Nimble."
He said Nimble's hybrid set up performed as well as the AFA, and both proved more than adequate for NISC's workload.
"We weren't approaching the performance ceiling on either array with our production workload," he said. "The highest workload on either array was about 800 megabytes per second, and we got sub-millisecond latency on both arrays."
Vollrath said Nimble's scalability convinced him to stick with the CS460 arrays. "Nimble can scale out and scale up," he said. "We've done both. We find it challenging to predict storage needs of NISC's business from year to year. Nimble lets us add cache for performance and less costly spinning disk when less performance is needed. So we can scale for capacity independent of performance and performance independent of capacity."
Vollrath said NISC took available of Nimble's easy scalability soon after installing the first arrays, and then again over the past year. "As we were migrating to Nimble we quickly exceeded storage capacity," he said. "We decided to scale out and added another CS460 and grouped them together as a single cluster. Last year we scaled up in Lake St. Louis with capacity and flash. We scaled up in North Dakota [in February 2015] by doing the same, adding flash and capacity."
Before installing Nimble, NISC used NetApp FAS arrays for primary storage. It still uses NetApp for file storage, with the iSCSI Nimble Storage arrays serving as block storage. Vollrath said NISC is about 98 percent virtualized on VMware vSphere 5.5, and has about 500 virtual machines. The Nimble arrays are mostly used to run Microsoft SQL and Exchange, but NISC also has Oracle, Progress and PostreSQL databases. Vollrath said Nimble's performance with VMs is another reason he selected its arrays.
"When we first selected NetApp [in 2010] we were starting to get into virtualization and didn't know exactly what we needed," Vollrath said. "NetApp was feature rich. As we got deeper into virtualization, we wanted a storage array that would do more management from the hypervisor and less from the array. We wanted an array were we could carve out volumes, present them to [VMware] vCenter and manage them in vCenter. The way Nimble scales out, when you add another array it still looks like a single array. You manage it from a single pane of glass and carve out individual volumes that stripe across both arrays. As you add arrays and capacity, it self-levels, and spreads the workload for you."
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