by Don Jones

Cloud computing may offer new flexibility in how we host Web-based services, but it also brings some substantial new challenges. The common theme of these challenges is one of managing performance and service delivery.

For example, in a traditional computing environment, you typically have direct control over all computing resources involved in delivering a particular service. You can control everything from the client application to the back-end database, from the network infrastructure itself to supporting services like directories and disaster recovery tools. You can measure the performance of these various elements, and use your own intelligence and experience to gauge when performance is becoming unacceptable.

In a cloud computing environment, however, you give up a level of this control as resources move into the cloud-based hosting environment. In a typical cloud-based application, you are at a minimum giving up control over your back-end database and application layer; in a purely Web-based application you’re giving up control over the client layer, too, meaning the entire application is out of your hands.

Your first thought might be, “well, that’s no problem – I just have to get a solid Service Level Agreement (SLA) from the cloud provider.” Not so fast. Amazon’s Elastic Compute Cloud (EC2) SLA says the company will:

… use commercially reasonable efforts to make Amazon EC2 available with an Annual Uptime Percentage (defined below) of at least 99.95% during the Service Year. In the event Amazon EC2 does not meet the Annual Uptime Percentage commitment, you will be eligible to receive a Service Credit…

Wow, “commercially reasonable efforts?” That’s reassuring. And yes, if they fail to live up to this rather vague promise you can get a service credit. But what about the damage to your business as a result of a cloud service outage? If your company is losing hundreds or thousands of dollars — or more — per hour because your Amazon-hosted application isn’t available, a “service credit” isn’t going to make a dent in that loss.

Most cloud provider SLAs also only cover full outages; they do not typically make a performance guarantee. That means that a slow cloud-based application falls within the provider’s SLA. That’s reasonable, since many factors that lead to a slow application are entirely outside the provider’s control, such as your application code.

So the big challenge with cloud computing is in providing the same level of performance and service management that you would provide for an entirely in-house service. In other words, you need to be able to monitor performance yourself, rather than trusting your cloud provider’s word for it. You need to know when access to your cloud-based application is, for example, slow from a particular location in the world, or when it’s slow for all users, and so on. How do you do that when so much of the application architecture is entirely outside your control?

By not focusing so much on the application architecture, at least not initially. Too many of us in IT don’t focus on the end user experience, or EUE, and that’s where our first metric should come from. How long does it take a user to complete a specified transaction? How long is each bit of delay — sending the request to the server, the server requesting data from the database, the server modifying that data, sending it back to the database, and sending a result to the client — involved in the transaction? By measuring the EUE, we can not only get a good idea of our application’s real-world performance, but we can also get some insight into where delays are occurring. This is possible even with cloud-based applications, although you’ll likely have to acquire or build new measurement tools to obtain EUE metrics.

About the Author

Don Jones has more than a decade of professional experience in the IT industry. He's the author of more than 30 IT books, including Windows PowerShell: TFM; VBScript, WMI, and ADSI Unleashed; Managing Windows with VBScript and WMI; and many more. He's a top-rated and in-demand speaker at conferences such as Microsoft TechEd and TechMentor, and writes the monthly Windows PowerShell column for Microsoft TechNet Magazine. Don is a multiple-year recipient of Microsoft's "Most Valuable Professional" (MVP) Award with a specialization in Windows PowerShell. Don's broad IT experience includes work in the financial, telecommunications, software, manufacturing, consulting, training, and retail industries and he's one of the rare IT professionals who can not only "cross the line" between administration and software development, but also between IT workers and IT management. Don is a co-founder of Concentrated Technologies, and serves as author and series editor for Realtime Publishers.