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Cloud bursting -- a deployment model in which an application runs in a private cloud until demand spikes and it "bursts" into a public cloud -- was an often-cited early use case for the cloud.
But while it sounds good in theory, it hasn't gained much traction in the real world. That's because it's difficult to pull off for most applications, mainly because it's hard to move storage in and out of the cloud.
"The problem is, people found it to be harder than expected," said Mike Matchett, senior analyst and consultant at Taneja Group. "You could spin up the compute but you couldn't get the storage up there and in and out of the cloud and pay for it persistently."
The advantage of cloud bursting is that an organization only pays for the extra resources when they are needed. Applications and storage move in and out of the public cloud depending on traffic and resource needs. But moving storage in and out of the cloud requires a lot of bandwidth, which can drive costs up.
"Storage is not easy to move back and forth into the cloud. It's a much less flexible resource," said Andrew Reichman, an analyst at ReichmanIT. "The whole application runs either on-premises or in the public cloud. It's not a question of which portion runs in the cloud. It's about pure capacity."
Experts recommend cloud bursting for high-performance, non-critical applications that handle non-sensitive information. An application can be deployed on-premises and then burst to the cloud to meet peak demands or the application can be moved to the public cloud to free up resources for business-critical applications. Cloud bursting works best for applications that don't depend on a complex application delivery system infrastructure.
"Cloud bursting is a thing people talk about a lot but I've never seen it in action. I can't point to any major customer examples," said Reichman, who previously worked as a marketing lead at Amazon Web Services (AWS). "When I was at Amazon, they didn't want to talk about cloud bursting that much because it's not a good use case."
Cloud bursting is always a hybrid cloud deployment, which means customers need to maintain an on-premises infrastructure while also purchasing public cloud resources. The application and its resources switch over to the public cloud when demand is high and moves back on-premises when demand is low.
Some storage vendors have partnered with colocation providers to help with issues surrounding bandwidth. NetApp offers its Private Storage for Cloud, in which a private NetApp infrastructure is collocated in worldwide Equinix data centers. Applications can run in the AWS, Microsoft Azure or IBM SoftLayer public clouds with a dedicated connection to NetApp storage. EMC also has a hybrid cloud service that connects storage on Isilon NAS arrays with Azure through Equinix.
Cloud bursting remains complicated for storage
"If the cloud environment looks like your on-premises environment, it's easier to cloud burst," Taneja Group's Matchett said. "For instance, you run VMware and burst it to another VMware cloud. But you have to set it up and I still have to pay for Opex. Plus, there are application-level issues. Amazon offers 80 different services. Your application can be built using all of them. If the application is complex enough that you configure [multiple] services around it, then it's hard to set up bursting."
Reichman recalled one Amazon customer -- a state government -- that tested cloud bursting for daily public reports about the system that handled its traffic camera application. That was a varied workload without security concerns and no customer data was used. The agency adopted cloud bursting because it had legacy systems on-premises that it didn't want to upgrade. However, the cloud bursting model was set up as a temporary solution until the entire application moved to the cloud.
"Even the CIO agreed that it made sense to run it all in the [public cloud]," Reichman said. "It was a way to prove it out and the next step was to run it fully in the cloud. It was a good way to test it out. Bursting is not an ideal long-term solution."
Mark Andersen, vice president of information technology at the Chicago-based Environmental Systems Design engineering firm, is not a fan of this type of hybrid configuration. Anderson uses the Nasuni Service to protect 15 TB of file data in the cloud, but doesn't burst it there.
"I'd either have everything in the cloud or nothing," he said. "Our applications are intense. I can't see part of it being farmed out at peak times. I don't think it's a fit for us. Performance is critical. I can't sacrifice performance for anything else."
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