Sun Microsystems March 26 filed a third lawsuit in federal court that extends the patent infringement charges to the storage management technology NetApp acquired from Onaro in January.

Other than a few candid comments in blogs and interviews by company executives on both sides, the new lawsuit was the first official public move by either company in the case since December.

The March 26 filing alleges patent infringement related to Onaro's SANscreen software that NetApp acquired in January, Sun spokesperson Dana Lengkeek told eWEEK. 

SANscreen, which was deployed in 32 percent of Fortune 50 companies at the time of the acquisition, allows enterprises to manage large amounts of storage with a minimum of downtime.

NetApp CEO Dan Warmenhoven told eWEEK several days ago that the case was deep "in the discovery process" and that he didn't know when court dates for hearings would actually be set.

To read more about the legal battle between Sun and NetApp, click here.

The latest Sun filing is part of the response to the lawsuit NetApp originally filed against Sun on Sept. 5, 2007 to forestall competition from the free ZFS (Zettabyte File System) technology, which Sun released to the open-source community in 2005.

NetApp claims Sun's ZFS, a speedy, industrial-strength storage file system included in Sun's Unix-derived OpenSolaris operating system, is patterned directly after its own WAFL (Write Anywhere File Layout) file system.

Sun, which claims to have created ZFS long before it released the code to the open-source community, filed counterclaims on Oct. 25 against the entire NetApp product line, seeking both injunctions and monetary damages.

The legal affidavit was filed in an East Texas court, as was the original NetApp action. Both companies have since agreed to move the court case to California, since all the principal players and inventors of the IP are in that state.

"ZFS is an extraordinary innovation, so threatening to NetApp's business model, they are seeking to remove it from the marketplace," Sun lawyers wrote Oct. 25 in a statement posted on the company Web site.