AWS fends off 'bouncy' cloud computing performance perception

Some Amazon Web Services customers blame 'noisy neighbors' for fluctuating cloud performance, but AWS officials say that's not what's happening.

Amazon Web Services shops said they've seen fluctuating performance on the company's Elastic Compute Cloud due...

to "noisy neighbors," but Amazon officials said that's a misconception.

A "noisy neighbor" in the context of cloud computing refers to a co-tenant on a piece of virtualized server hardware that hogs resources, slowing other tenants' virtual machines down in the process.

"The Achilles' heel for Amazon is the noisy neighbor," said Devon Lazarus, cloud services manager for an electronic equipment manufacturer on the West Coast.

Lazarus said the key to avoiding this problem is to pick the largest appropriate instance type to run performance-sensitive applications -- that way, in theory, the application shares a server with fewer other machines.

"The micro and small instances are not for production," he said. "We usually use them for testing and validation, then move into larger instances."

The Achilles' heel for Amazon is the noisy neighbor.
Devon Lazaruscloud services manager for an electronic equipment manufacturer on the West Coast

Another Elastic Compute Cloud (EC2) customer, who asked to remain anonymous, also said he has seen the noisy neighbor problem when it comes to network bandwidth.

These comments came on the heels of a survey by Cloud Spectator, commissioned by AWS competitor Virtustream, which ranked Amazon Web Services (AWS) at the bottom of a list of competitors in cloud computing performance. Since the survey was commissioned by a competitor, it is to be taken with a grain of salt, but it is also one data point in support of customers' perceptions about EC2 performance.

Meanwhile, AWS officials said that while performance may vary, there is no noisy neighbor problem in EC2.

"What customers are really reporting there is a difference in performance from one instance to another, but it's not due to other people [sharing the hardware]," said Matt Wood, general manager of data science for AWS.

Instead, Wood said, Amazon might have refreshed its host hardware, so customers might see an instance restart on a server with a faster processor and conclude that the previous host suffered from contention problems.

"At a high level, we have hard partitioning at the CPU level, and we provide [Provisioned IOPS]- and [Elastic Block Storage]-optimized instances to ensure consistent IO performance," Wood said. "On C3 instances, we also have single-root IO virtualization, which enhances networking further."

But analysts say customers' observations have some merit.

"Noisy neighbor" is only supposed to apply to situations where resources are oversubscribed, which is typical for Web hosting and virtual private servers, said Carl Brooks, analyst with the 451 Group based in Boston. AWS does not oversubscribe, so this shouldn't happen.

"What happens instead is that other parts of the host system get overtaxed -- RAM, bandwidth, traffic to disk," Brooks said. "As AWS pointed out, they have additional for-pay services to mitigate that effect, but that doesn't change the user's experience. It's not technically a noisy neighbor, but it is your neighbors being too noisy overall."

Some customers at the show said fluctuations in cloud computing performance must be expected from any service provider, and the appropriate response is just to spin up more instances.

"Spot instances are two cents apiece -- what do I care about having to spin up more?" said Brian Tarbox, a software engineer at Cabot Research, a financial data analysis firm based in Boston. "You have to assume failures happen and that there will be bouncy latency and throughput; you have to build systems that can handle those things."

About the author:
Beth Pariseau is senior news writer for SearchCloudComputing.com. Write to her at bpariseau@techtarget.com or follow @PariseauTT on Twitter.

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"Another Elastic Compute Cloud (EC2) customer, who asked to remain anonymous, also said he has seen the noisy neighbor problem when it comes to network bandwidth."

Well, I can see why s/he'd wish to rename anonymous. Unless that individual has some insider information, s/he likely hasn't seen anything firsthand. It's speculation...and harmful at that.
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""Noisy neighbor" is only supposed to apply to situations where resources are oversubscribed, which is typical for Web hosting and virtual private servers, said Carl Brooks, analyst with the 451 Group based in Boston. AWS does not oversubscribe, so this shouldn't happen."

Noisy neighbours can happen for a lot of reasons. Even if a provider does not oversubscribe (which i translate as not assigning more than 1 virtual core to 1 physical core), there is still the problem of fluctuating performance due to neighboring cores. If a VM runs on a core of a dual core processor in a standalone way (because there is no demand currently for the other core), its performance is significantly better than when another VM is executing on the other core of the processor due to RAM, cache contamination etc. Thus, activating and deactivating this second VM frequently would result to a performance deviation for the original VM
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First:
"AWS officials said that while performance may vary, there is no noisy neighbor problem in EC2."

with the explanation:
"Amazon might have refreshed its host hardware, so customers might see an instance restart on a server with a faster processor and conclude that the previous host suffered from contention problems."

Translation:
We upgraded your hardware. For free. You're welcome.

The truth of the situation is somewhere in the middle - some latency problems are based on user perception, some are based on the inherent latencies built into accessing applications on shared hardware over a not necessarily optimized network, and some are, indeed, due to noisy neighbors.

The problem is that AWS is a black box, and without an end to end performance analysis, all users see is an unexplained slowdown. As long as the problem doesn't rise above the level of a nuisance, AWS can afford to ignore it. If the problem becomes more of an issue, AWS will need to address it, or start seeing its customers look for other solutions.
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