The response times represent not only the cloud service's ability to respond from a given data center, but all the latencies of the last mile of service as the message moves off the Internet backbone and onto a local network segment. (Cloud vendors have no control over those latencies.) The results are an average for each vendor, a composite response time compiled from 90,000 browser calls a month to the target application placed in each service provider's cloud.

In that sense, the response times reflect what end users are likely to see "at the edge of the network," not the optimum performance of each cloud vendor, noted Ryan Bateman, manager of application performance management products at Compuware, who blogged about the test results. If you run your application at the site of a cloud vendor that's in your locale, the response times will improve.

That's evident in the rest of the results. CloudSigma is a European cloud supplier, with data centers in Bern, Switzerland, and Frankfurt, Germany. Its times are higher, but so are those of EC2's service site in Ireland. That reflects a preponderance of test pings arising in the United States, although Willoughby said about 37% of the bots are resident on consumer computers outside the United States, and roughly reflect the origins of cloud traffic.

Compuware aired the results of fourth quarter monitoring of 15 vendors on Tuesday. The other public cloud vendors included were: Amazon EC2 West (in Washington State), sixth at 11.838 seconds; OpSource, the young cloud vendor in Santa Clara, Calif., seventh at 12.440 seconds; GoGrid West, eighth, 12.604 seconds; Terremark, ninth, 12.971 seconds; CloudSigma, tenth, 18.079 seconds; Amazon EC2 Europe/Ireland, eleventh, 18.161 seconds; Windows Azure for Southeast Asia, twelfth, 27.534 seconds; and Amazon EC2 Asia/Pacific Singapore, thirteenth, 30.965 seconds.

The CloudSleuth monitoring and measurement service was established after Compuware's acquisition of the Gomez Web application performance measuring system in October 2009. It paid $295 million for the acquisition, and now offers end-user experience monitoring as a service to corporations.

We need more tools like CloudSleuth to develop a realistic picture of what cloud services can and cannot do for the enterprise. Amazon offers its own CloudWatch, and there are additional third-party services, including VMware's Hyperic, and Apparent Networks' network segment monitor. The smart cloud user will put all of these tools to use to figure out what kind of service he's getting.

SEE ALSO:

Leading Developers Dismiss Charge That Cloud Is 'Vapor'

Microsoft Windows Azure Turns One, Still Growing Up

Integration In The Cloud, The Sleeper Issue

With Cloud, What You Don't Know Can Hurt You

Microsoft Needs A Wider Cloud Strategy

See all stories by Charles Babcock

Charles Babcock is an editor-at-large for InformationWeek.

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