Sun on Wednesday announced plans to offer its own Open Cloud Platform, starting with server and storage services aimed at developers who need an extended platform to produce a new application.

Sun expects to have cloud servers and storage available to customers by "this summer," where customers will run applications under Windows, Solaris or Linux in Sun VirtualBox virtual machines. Open Cloud Platform will compete with Amazon.com's Elastic Compute Cloud and S3 storage services.

The company revealed its plans at an event in New York, amid reports that IBM may be offering as much as $6.5 billion to acquire the rival's assets.

"We want to provide developers with a data center in the cloud. We want to give them a sense of control they've never had," said David Douglas, senior VP of cloud computing, in an interview.

But Sun's cloud will give developers the ability to both read and write to files from the browser window, something that's still denied of Amazon users, Douglas said. Sun's Cloud Storage Service will support the WebDAV protocol, an extension to HTTP, for file access. With WebDAV, it would be possible for a cloud user to have a spreadsheet application in the cloud and fill in data in the sheet without creating a new spreadsheet with each change.

"WebDAV allows a certain class of read/write applications over the Internet. WebDAV is perfect for that," Douglas said.

WebDAV was designed by the Internet Engineering Task Force to allow multiple users to make multiple changes to the same file. Douglas said Sun's support for WebDAV won't extend to multiple users working on the same file in its initial implementation.

Sun is working on a set of open source APIs for its cloud and is sharing them with the Eucalyptus Project, an effort to create an open source cloud structure compatible with Amazon's EC2. Eucalyptus developers have been able to create an Open Cloud Platform using Sun's existing API set, Douglas said.

Eucalyptus project developers were scheduled to appear with Sun officials on stage today in New York as it unveiled plans for its cloud project before CommunityOne, a Sun developer event.

Sun owns the open source MySQL database and plans to demonstrate backing up MySQL to the Sun cloud using a partner Zamanda's backup and recovery software. Sun acquired Q-Layer in January, a cloud startup that produced a staging system that could host a variety of operating systems for cloud applications.

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