Once upon a time a corporate data center included software and hardware from a handful of big-name companies and no one else.

But there's a major revolution going on. Companies are shipping more and more apps into the cloud and they are revamping their own data centers to be faster, more efficient, using new forms of databases, building what is known as "private data centers."

The result is a wide-open door for startups offering fresh technology.

With that in mind, we sifted through the buzz to come up with this list of hot companies. They offer interesting technology, or they've attracted big funding, or they have amazing founders ... or they have all of the above.

Rex Computing: Low-power servers built by a child prodigy

Company: Rex Computing

Funding raised: Unknown, but Rex Computing's cofounder, Thomas Sohmers, is a member of Peter Thiel's startup accelerator, the 20 Under 20 Thiel Fellowship. The accelerator grants $100,000 to kids to skip college and focus on their work.

Why it's hot: At the age of 17, Sohmers dropped out of high school to start this company with cofounder Kurt Keville. The two of them built a very powerful computer server using low-power ARM chips, the kind that run tablets and smartphones. ARM servers are a huge future trend for the data center.

Rex's servers were also designed for Facebook's game-changing hardware project known as the Open Compute Project. OCP is a project where big companies like Facebook and Microsoft have shared their hardware designs and opened the door for startups like Rex to sell to them.

CloudGenix: Stealthy Cisco networking startup

Company: CloudGenix

Funding raised: $9 million from Charles River Ventures and Mayfield Fund.

Why it's hot: CloudGenix, founded in 2013, is still in super stealth mode. But we know that it's working on a new form of networking that will make it faster to share data between data centers and offices.

CEO founder Kumar Ramachandran is a 13-year Cisco veteran who previously worked with Cisco's wide-area networking products. Instead of competing with Cisco, his startups tech can be bolted on top of Cisco products, giving him a huge market of companies that want to keep their Cisco networking equipment while making it better.

Splice Machine: A new kind of Hadoop database

Company: Splice Machine

Funding raised: $19 million from Mohr Davidow Ventures, InterWest Partners.

Why it's hot: The 2-year-old Splice is trying to do what those in the know said couldn't be done: turn the popular big data storage technology, Hadoop, into a kind of database that competes directly with Oracle (in geek speak, a SQL RDBMS on Hadoop).

Hadoop was always billed as a new kind of big data technology that collected the kind of stuff that wouldn't be put in a traditional database (photos, tweets, documents). It was never intended to replace the traditional database that stores precise rows and columns of data.

But this month Splice releases software to turn Hadoop into a regular database, with 15 beta customers already trying it out, it said.

CEO cofounder Monte Zweben has a long history in the tech industry. He started at NASA working with artificial intelligence and the Space Shuttle. He also founded two pre-Internet bubble companies, Red Pepper Software and Blue Martini.

Igneous Systems: Secretive cloud storage startup

Name: Igneous Systems

Funding raised: $26.6 million, led by New Enterprise Associates (NEA) with participation from Madrona Venture Group, Redpoint Ventures and Isilon Systems cofounder, Sujal Patel.

Why it's hot: They are stealth and say they won't talk much about their product until 2015 except to say that it has something to do with data center storage and the cloud. But they've already landed a healthy $23.6 million round for the product and people are watching them.

The founders come from Isilon Systems, bought by EMC in 2010 for about $2.25 billion, and NetApp.

See the rest of the story at Business Insider

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