Sun Microsystems has delayed support for two core features in its latest operating system, Solaris 10, executives have confirmed.

Sun argued that two of the key reasons to buy into the Unix variant, which launched late last year, are a new file system - ZFS (Zettabyte File System) - and a the Linux Application Environment, code-named "Janus", a feature allowing Linux applications to run unmodified on the operating system.

Last year, Sun said ZFS would ship in the second half of 2005, while Janus was to ship shortly after the Solaris 10 launch. That is no longer the plan, according to Glenn Weinberg, the vice president of Sun's operating platforms group.

"These features are not scheduled for specific updates at this time," he said in an online chat session late yesterday, responding to a query from industry journal "Our intent is that they will be released in (calendar year) 06."

Both features are still in the testing stage, said Chris Ratcliffe, a Solaris marketing manager, during the same online chat. Sun plans to deliver ZFS to customers via Solaris Express, a preview programme, by the end of this year, followed by an update release to the operating system "at a future date", he said. "We still have some finishing work to do," Ratcliffe said.

Sun is about to release a preview of Janus in order to get customer feedback, Ratcliffe said: "We will use that feedback to design a solution that we intend to deliver in an Update of Solaris 10."

ZFS is designed to simplify storage by removing the need to partition storage into slices, volumes and file systems. Janus is designed to make Solaris a more attractive prospect for those using or considering Linux, although Sun president and COO Jonathan Schwartz has remarked that the technology is not intended as a threat to Linux.

Sun is planning to complete the transition of Solaris to open source this summer, completing a programme begun last year.

A full transcript of the online chat is available here.