Sun Microsystems' legal counsel disclosed in the blogosphere Thursday that efforts to settle a patent infringement lawsuit filed against the firm by NetApp have so far been unsuccessful.

NetApp had filed the lawsuit last September alleging that Sun's ZFS file system technology infringes on seven of its patents.

In a blog post Thursday, Mike Dillon, Sun's executive vice president and general counsel, said that a settlement conference held Wednesday in the Northern District Court of California was "rather brief" and that "unfortunately, we weren't able to resolve the dispute."

NetApp declined comment on the blog post. When contacted, Dillon refused to answer questions about the post.

NetApp filed the lawsuit against Sun last year in US District Court in Lufkin, Texas, seeking unspecified compensatory damages and an injunction that would prohibit Sun from developing or distributing products based on its ZFS file system technology.

In his post, Dillon said that the US Patent and Trademark Office has re-opened the patent examination process on five NetApp patents included in the lawsuit at Sun's request. He added that Sun has so far convinced the patent office to reject one of the disputed patents.

Sun has since filed three lawsuits charging NetApp with violating multiple Sun patents. The third was filed after NetApp acquired Onaro in January.

Dillon contended in his post that NetApp has infringed on 22 Sun patents in a variety of products, including the FAS6000, FAS9000, FAS3000 and FAS2000 storage arrays, the V6000 virtualization system, the MetroCluster and SnapMirror disaster recovery software, the NearStore Virtual Tape Library and FAS platforms with SATA drives, noted Dillon.

Analysts have predicted that the NetApp and Sun legal skirmish over ZFS could escalate into a major test case for open-source software. In an April court filing against a Sun motion for partial stay in the lawsuit, NetApp founder Dave Hitz said he is "painfully aware that IP litigation is not favorably viewed by many members of the open-source community." In the court document, Hitz accused Sun of launching a smear campaign by contending that NetApp is stifling open-source efforts.