Cloud versus cloud: A guided tour of Amazon, Google, AppNexus, and GoGrid

Cloud computing offerings differ in depth, breadth, style, and fine print; beneath the heady metaphor lurk familiar pitfalls, complex pricing, and many questions

Who wouldn't want to live in a "cloud"? The term is a perfect marketing buzzword for the server industry, heralding images of a gauzy, sunlit realm that moves effortlessly across the sky. There are no suits or ties in this world, just toga-clad Greek gods who do as they please and punish at whim, hurling real lightning bolts and not merely sarcastic IMs. The marketing folks know how to play to the dreams of server farm admins who spend all day in overgrown shell scripts and impenetrable acronyms.

To test out these services, I spent a few days with them and deployed a few Web sites. I opened up accounts at four providers, configured some virtual servers, and sent Web pages flowing in a few hours. Our choice of four providers wasn't as scientific as possible because there are a number of new services appearing, but I chose some of the big names and a few new services. Now, I can invoke Joni Mitchell and say I've looked at both sides of these services and offer some guidance.

[ Download a QuickTime video tour of each compute cloud: Amazon EC2 | Google App Engine | GoGrid | AppNexus. See also: Inside Amazon Web Services, Windows Azure Services Platform gives wings to .Net, First Look: Google's high-flying cloud for Python code, and What cloud computing really means. ]

The first surprise is that the services are wildly different. While many parts of Web hosting are pretty standard, the definition of "cloud computing" varies widely. Amazon's Elastic Compute Cloud offers you full Linux machines with root access and the opportunity to run whatever apps you want. Google's App Engine will also let you run whatever program you want -- as long as you specify it in a limited version of Python and use Google's database.

The services offer wildly different amounts of hand-holding, and at different layers in the stack. When this assistance works and lines up with your needs, it makes the services seem like an answer to your prayers, but when it doesn't, you'll want to rename it "iron-ball-and-chain computing." Every neat feature that simplifies the workload does it by removing some switches from your reach, forcing you into a set routine that is probably but not necessarily what you'd prefer.

After a few hours, the fog of hype starts to lift and it becomes apparent that the clouds are pretty much shared servers just as the Greek gods are filled with the same flaws as earthbound humans. Yes, these services let you pull more CPU cycles from thin air whenever demand appears, but they can't solve the deepest problems that make it hard for applications to scale gracefully. Many of the real challenges lie at the architectural level, and simply pouring more server cycles on the fire won't solve fundamental mistakes in design.

By the end of my testing, the clouds seemed like exciting options with much potential, but they were far from clear winners over traditional shared Web hosting. The clouds made some things simpler, but they still seemed like an evolving experiment.

[ Jump to the reviews and the analysis: Amazon EC2 | Google App Engine | GoGrid | AppNexus | The fine print | Crashing the cloud metaphor | Best and worst ]

Amazon Elastic Compute Cloud

Amazon was one of the first companies to launch a product for the general public, and it continues to have one of the most sophisticated and elaborate set of options. If you need CPU cycles, you can spin up virtual machines with Elastic Compute Cloud (EC2). If it's data you want to store, you can park objects of up to 5GB in the Simple Storage Service (S3). Amazon has also built a limited database on top of the S3, but I didn't test it because it's still in a closed beta. To wrap it up, your machines can talk among themselves with the Simple Queue Service (SQS), a message-passing API.

All of these services are open to the Web and accessible as Web services. There's a neat demo for the SimpleDB that is just a pile of HTML running in your browser while querying the distant cloud. The documentation is extensive, and Amazon makes it relatively easy to wade through the options.

The ease, though, is relative because almost everything you do needs a command line. Amazon built a great set of tools with sophisticated security options for sending orders to your collection of machines in the sky, but they all run from the command line. I found myself cutting and pasting commands from documentation because it was too easy to mistype some certificate file name, for example.

Unix jockeys will feel right at home in this world because the virtual machines at your disposal are all versions of Linux distros like Fedora Core 4. After you grab one off the shelf, you can install your own software and create a custom instance that can be loaded relatively quickly if there's space available in the cloud.

It's hard to go into enough detail about all of the offerings described here, but Amazon is the most difficult because it has the most extensive solutions. Amazon is thoroughly committed to the cloud paradigm, rethinking how we design these systems and producing some innovative tools. [ See the QuickTime video. ]

[ Jump to the reviews and the analysis: Amazon EC2 | Google App Engine | GoGrid | AppNexus | The fine print | Crashing the cloud metaphor | Best and worst ]

Google App Engine

Google's App Engine is a polar opposite of Amazon's offering. While you get root privileges on Amazon, you can't even write a file in your own directory with the App Engine. In fact, it's not even clear that you get your own directory, although that's probably what's happening under the hood. Google ripped the file write feature out of Python, presumably as a quick way to avoid security holes. If you want to store data, you must use Google's database.

The result of all of these limitations is not necessarily a bad thing. Google has stripped Web applications down to a core set of features and built up a pretty good framework for delivering them. I was able to write a simple application with several hundred lines of Python (cutting and pasting from Google's documentation) in less than an hour. Google offers some nice tools for debugging the application on your own machine.

Deploying this application to the cloud should have taken a few seconds, but it was held up by Google's insistence that I fork over my cell phone number and wait around for a text message that tests the number. When my message didn't show up for several hours after retrying, I switched to a friend's phone and finally activated my account.

Google insists on linking your App Engine account to both your cell phone and your Gmail account because -- well, I don't know. I think it's to track down the scammers, spammers, pharmers, phishers, and other fraudsters, but it starts to feel a bit creepy. Maybe it will help customer service and allow them to field support requests with answers like, "Your cell phone shows you filed this report from a location with a liquor license. Your e-mail suggests you're coding while waiting for Chris to get off of work. We suggest going home, sleeping this off, and then it will take you only a few seconds to find the endless loop on line 432 of main.py. BTW, Chris is lying to you and is really out with someone else."

The best users for the App Engine will be groups, or most likely individual developers, who want to write a thin layer of Python that sits between the user and the database. The API is tuned to this kind of job. In the future, Google may add more features for background processing and other services such as lightweight storage, but for now, that's the core strength of the offering. [ See the QuickTime video. ]

GoGrid
GoGrid refers to itself as the "world's first multi-server control panel." GoGrid's offerings aren't functionally different from Amazon's EC2, but using the old term "control panel" seems to be a better description of what's going on than the trendier term "cloud." You start up and shut down load balancers in much the same way as relatively ancient tools like Plesk and cPanel let you add and subtract services.

While GoGrid offers many of the same services as Amazon's EC2, the Web-based control panel is much easier to use than the EC2 command line. You point and click. There's no need to cut and paste information because little pop-up boxes show the way, by suggesting available IP addresses, for example. The system is intuitive, and it takes only a few minutes to build up your network. A simple ledger on the left keeps track of the costs and helps you manage the budget.

GoGrid also has a wider variety of OS images ready to go. There is the usual collection of CentOS/Fedora and common LAMP stacks. If you need Windows, you can have Windows Server 2003 with IIS 6.0, and Microsoft SQL Server is available at extra cost. There are also images with Ruby on Rails, PostgreSQL, and the Facebook application server. These make it a bit easier to start up.

While GoGrid offers many of the same features as Amazon's EC2, it doesn't provide more cloudlike services for storing information in a shared way like SimpleDB. This can make it a bit harder to start up and shut down servers without a bit of grief. The startup notes for the service point out that the only way to stop paying for a server is to delete it, and that means losing all of the data on it.

There's no simple way to build custom images at this moment, but the documentation says GoGrid is working on a way to turn any running server into an image that can be restarted later. If you're going to be expanding and contracting your network as the traffic ebbs and flows, you'll have to come up with some tools of your own to add and subtract these servers. [ See the QuickTime video. ]

AppNexus
If you like the idea of the cloud but aren't sure if you want to leave behind the old trustworthy world of Unix, cron jobs, and other tools, then AppNexus is a service that aims to be a bit more transparent. The company has taken a big, industrial-sized server farm with the best load-sharing tools and storage boxes and found a way to let you buy it in small portions. AppNexus provides a number of command-line abstractions that let you turn servers on and off, but they also let you drill down into the file system.

The main functions of the AppNexus cloud are similar to Amazon's EC2. You log in through a command line and boot up images of Linux distributions. AppNexus says it can rebuild images from other sources like Amazon's EC2 by replacing the kernel with a version that's more aware that it is running in a virtual environment. Then it just takes a few key clicks on a command line to set up a load balancer.

One open question in the world of cloud computing is where the abstraction occurs; that is, where do the walls between the machines become blurred and it all starts to look a bit cloudy? Amazon's SimpleDB hides the storage behind a software wall and gives you access to it through some Web service call. AppNexus is working at a lower level by building in a cluster of Isilon IQ X-Series storage clusters into its cloud.

This gives you the option of simply mounting the storage and sharing the data across your cluster of servers -- if you consider that simple. Instead of working with abstract keys, you use real file names as the keys. The cluster handles the rest of the work.

A better solution is to use what AppNexus calls its CDN, or Content Delivery Network. The storage cluster has its own set of HTTP servers built in, and you can automatically begin serving static data from your files. Just write the files to the /cdn directory and they become available. AppNexus will distribute this storage cloud to multiple datacenters, making it simpler to serve up the static data from the closest location. [ See the QuickTime video. ]

The fine print
One of the ways to go truly insane is to read the terms of service for these clouds. While the people who wrote the old co-location contracts could try to imagine the data as living on a single server that was in a certain box owned by a certain person and residing in a certain jurisdiction, all bets are off with a cloud. The whole point is that it isn't confined to one box, one building, or even one country.

Some of the service agreements are very specific and clear. GoGrid, for instance, spells out numerical thresholds for standard values such as latency, jitter, and packet loss for the six continents. If the cloud doesn't meet them, GoGrid promises to give you service credits for 100 times the amount lost.

Other terms are deliberately murky. You might consider it fairly capricious for Amazon to demand the right to terminate your account "for any reason" and "at any time," but the company also carefully reserves the right to terminate your account for "no reason" too. In other words, "It's not you, honest. It's me. No. I take that back, it's not even me. It's just over between the two of us. No reason."

Google's terms seem more generous, indicating it will terminate accounts only if you breach the terms of the agreement or do something unlawful. But Google does reserve the right to "pre-screen, review, flag, filter, modify, refuse, or remove any or all Content from the Service." I want to say that the terms seem more reasonable than they were when I read them several weeks ago, but I can't be sure. And it doesn't matter too much because new terms apply whenever Google wants to change them, and you signify your acceptance by continuing to use the service.

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