Who provides what in the cloud

InfoWorld - The news that AT&T Inc. has joined the rapidly growing ranks of cloud computing providers reinforces the argument that the latest IT outsourcing model is well on its way to becoming a classic disruptive technology.

By enabling data center operators to "publish" computing resources -- such as servers, storage and network connectivity -- cloud computing provides a pay-by-consumption scalable service that's usually free of long-term contracts and is typically application- and operating system-independent. The approach also eliminates the need to install any on-site hardware or software.

Currently dominated by Amazon.com Inc. and several small start-ups, cloud computing is increasingly attracting the interest of industry giants, including Google, IBM and now AT&T. "Everyone and their dog will be in cloud computing next year," predicts Rebecca Wettemann, an analyst at Nucleus Research, a technology research firm.

Yet James Staten, an analyst at Forrester Research Inc., warns that prospective adopters need to tread carefully in a market that he describes as both immature and evolving. Staten notes that service offerings and service levels vary widely among cloud vendors. "Shop around," he advises. "We're already seeing big differences in cloud offerings." To help cut through the confusion, here's a rundown of some major cloud providers -- both current and planned -- all offering resources that go beyond basic services such as software-as-a-service applications and Web hosting:

3Tera Inc.: Appliance-driven virtual servers

3Tera's AppLogic is a grid engine that has evolved over time into a full-fledged cloud computing environment. The company said its offering is designed to enable data centers to replace expensive and hard-to-integrate IT infrastructure -- such as firewalls, load balancers, servers and storage-area networks -- with virtual appliances. Each appliance runs in its own virtual environment.

AppLogic combines servers into a scalable grid that's managed as a single system via a browser or secure shell. According to 3Tera, data centers can add or remove servers on the fly, monitor hardware, manage user credentials, reboot servers, install software, build virtual appliances, back up the system, repair damaged storage volumes, inspect logs and perform every other management task from a single point of control, all while the system is running.

Amazon.com: As-you-need-them basic IT resources

Amazon was an early cloud computing proponent, and the company now has one of the market's longest menu of services. Amazon's core cloud offering, the Elastic Compute Cloud (EC2), provides a virtualized cloud infrastructure that's designed to provide scalable compute, storage and communication facilities.

Amazon's cloud computing arsenal also includes the Simple Storage Service (S3), a persistent storage system; the Simple Database (SimpleDB), which provides a remotely accessible database; and the Simple Queuing Service, a message queue service that's also an agent for tying together distributed applications created by the EC2, S3 and SimpleDB combo.