This is a guest post from Larry Dignan of TechRepublic’s sister site ZDNet. You can follow Larry on his ZDNet blog Between the Lines, or subscribe to the RSS feed.

I’ll be a judge Friday on the data management panel at the Under the Radar conference, an American Idol-ish bake-off for cloud computing startups. My assignment: Do a little homework on the companies I’ll be judging.

The companies — Axcient, Ctera, Engyte, and Sonian — have a common theme: Online cloud storage backup for small and medium sized businesses.

Where they differ is their approaches. For instance, Axcient touts that it doesn’t need software. Axcient is a storage appliance that backs up data on its hardware and in the cloud. The target is small and mid-sized businesses.

Ctera has a similar theme with one key twist: The company expects to be bundled as a service sold by telecom and broadband providers. That’s a helluva a channel. Ctera has a neat little device called the CloudPlug that can turn any external USB drive into a network file server with online backup. 

Both of those aforementioned companies clearly see appliances and the cloud being a big selling point.

Egnyte has a similar plan, but leverages the hard drive that customers already have. Engyte is a software based service the turns a drive into a cloud connected file server. Egnyte is picking the local cloud that bridges online and on-premise storage. 

The big question for Axcient, Ctera and Egnyte is how do they plan to compete with larger players, notably EMC, which is pursuing a similar SMB market by connecting Mozy and Iomega together. 

And then there’s Sonian, which targets larger businesses-mid-sized and up-looking for e-discovery help. I still need to bone up on Sonian a bit, but it already gets props for picking the hottest market. E-discovery is a big deal for compliance-burdened companies looking to archive email and other regulatory requirements (see TechRepublic special report). 

Sonian has gone completely the enterprise 2.0 route and has built its business on Amazon’s cloud architecture. The challenge for Sonian is the same as the others: How do you compete with larger players and convince customers that you’ll be around?

In any case, it should be an interesting bunch of presentations. Should you have any questions for these folks drop them in the talkback below.