A mainframe version of the OpenSolaris operating system is now available for download, IBM and Sun announced Monday.

Both Solaris and the System z mainframe have a huge footprint in the financial services sector, and many customers will be interested in consolidating Solaris-based applications onto mainframe servers, says Forrester Research analyst Brad Day.

Mainframes are already attractive for Linux consolidation projects and now IT shops are likely to say "I can take one big mainframe and virtualize it into a bunch of little Solaris servers," Day says. IBM and Sun say the initiative will allow custom C/C++ applications based on Solaris to be migrated from Sun hardware to System z.

IBM and Sun call the mainframe port a prototype and urge open source developers to participate in the project and help improve the software. The prototype was designed by Sine Nomine Associates, a research and engineering firm, with financial and technical support from IBM and Sun.

Sine Nomine also is developing a Java software port for the mainframe, which should be available in late 2009 or early 2010, Day says. While many mainframe users will be interested in testing out the OpenSolaris download, they'll wait for the Java port before putting anything into production, he says.

"For this to be compelling it can't just be the Solaris kernel," Day says. "It has to be the entire Java environment. This is a work in progress."

Sun's Solaris operating system is used for many client-facing Internet-based applications as well as mission-critical applications like SAP and Oracle. Solaris has gained popularity by being flexible to enough to run on a variety of servers, both Sun and non-Sun platforms and both Sparc and x86 servers, Day says.

IBM and Sun demonstrated an early version of the OpenSolaris code base running on the mainframe in November 2007. The IBM/Sun partnership also includes an agreement for Solaris to run on x86 servers and blades, and an IBM endorsement of Sun's xVM virtualization initiative.

OpenSolaris runs within the mainframe's virtualization technology, known as z/VM, which allows the creation of thousands of virtual images on a single hypervisor.